Nine times in the Book of Acts, the word “bold” in its various forms is used to describe the Apostles and their associates.  Indeed, the entire book chronicles the bold acts of the Apostles, primarily those of Peter and Paul. One only need to read Peter’s address to the Pharisees in chapter 4 to observe this. Peter stands before the Pharisees – the very same ones who barely two months prior had Jesus crucified – and (filled with the Holy Spirit) says, “…by the name of Jesus Christ of Nazareth, whom ye crucified, whom God raised from the dead, even by him doth this [formerly paralyzed] man stand before you whole.”  Boldly proclaiming the truth and exposing error, they were following in the footsteps of Jesus, Who called the Pharisees “hypocrites,” “sons of hell,” “blind guides,” “fools and blind,” “whited sepulchres,” “serpents,” and “generation of vipers.” 
The Greek word translated as ‘bold’ is a compound word which could be translated literally as all outspokenness; that is, frankness and bluntness. We typically think of boldness as the demeanor of a person, someone who is fearless, confident, or sure of himself. But its definition and the passages cited below link the Apostles’ boldness moreso to their speech than to their comportment, though the two are related. They knew what they believed, and they spoke it plainly and clearly.
Let’s look at some Scriptures and note the tie between the Apostles’ boldness and their speech.
“Now when they saw the boldness of Peter and John…” ~Acts 4:13
How did the priests see Peter and John’s boldness? It was demonstrated through their clear proclamation of the power of the Name of Jesus and of salvation through Him alone, which is recorded in verses 8-12.
“And now, Lord, behold their threatenings: and grant unto thy servants, that with all boldness they may speak thy word…” ~Acts 4:29
After their confrontation with the priests, Peter and John return to the other disciples and tell them of the threats they received. The disciples then pray for boldness to speak God’s Word. God answers their prayer by empowering them with the Holy Spirit to continue proclaiming the Gospel boldly. 
Acts 9:27 and 29 records how Paul “preached” and “spake boldly in the Name of the Lord Jesus.”
“But Barnabas took him (Paul), and brought him to the apostles, and declared unto them how he had seen the Lord in the way, and that he had spoken to him, and how he had preached boldly at Damascus in the name of Jesus… And he spake boldly in the name of the Lord Jesus, and disputed against the Grecians: but they went about to slay him.” ~Acts 9:27, 29
An immediate result of Saul of Tarsus’ conversion is the possession of boldness to preach in the Name of the same Jesus Whom he previously tried to destroy. 
Here are the rest of the references.
“Then Paul and Barnabas waxed bold, and said…” ~Acts 13:46
“Long time therefore abode they (Paul and Barnabas) speaking boldly in the Lord…” ~Acts 14:3
“And he (Apollos) began to speak boldly in the synagogue…” ~Acts 18:26
“And he (Paul) went into the synagogue, and spake boldly for the space of three months, disputing and persuading the things concerning the kingdom of God.” ~Acts 19:8
After each of these occurrences, what followed was a clear, uncompromising, unadulterated message which its hearers were forced to either accept or reject.
What were some of the results of their boldness?
- People were saved and the Gospel spread.  They spread the Gospel so far and wide in their day, it was said that they “turned the world upside down.” 
- The saints were edified. 
- This may imply that if the Apostles had not been bold and clear in proclaiming the Gospel, these things would not have happened. And the same goes for us: if we want to see sinners saved and the saints taught and built up in the faith, then we must, by the power of the Holy Spirit, be bold and clear, faithfully preaching the Gospel, which is the power of God for saving souls. 
- Speaking the Word boldly, however, can also lead to one making enemies and to persecution.  This is to be expected from a world hostile to God, His Gospel and His servants. Both Jesus and the Apostles told us to expect it.  Gospel ministry is certainly not for the faint of heart. There will be opposition. Expect it, be prepared for it.
- In that persecution, however, we can have joy. This was said of the disciples  and should be true of us as well. Having boldness and suffering persecution does not mean that we have to be sour puss Christians. On the contrary, we can be joyful in the midst of it. Joy is a natural byproduct of the Holy Spirit’s sanctifying work in our lives,  and it is the result the persecution is intended by God to produce. 
Pastor Jordan Hall is right when he says, “God has not called us to nuance or creativity. God has called us to clarity.”  May God grant us this boldness, and may we leave the results of our preaching to God, having confidence that His Word will achieve the purpose for which He sends it. 
 Acts 4:13, 29, 31; 9:27, 29; 13:46; 14:3; 18:26; 19:8
 Acts 4:10, italics added for emphasis
 Read Matthew 23:13-33
 Acts 4:31
 Acts 26:9
 Acts 13:48-49; 19:10
 Acts 17:6
 Acts 18:26; 9:31
 Romans 1:16
 Acts 9:23, 29; 13:50; 14:5
 Matthew 5:10-12, 10:17-39; Acts 14:22; Philippians 1:29; 2 Timothy 3:12; 1 Peter 4:12-19; 1 John 3:13
 Acts 13:52
 Galatians 5:22
 1 Peter 4:13
 stated in a recent podcast, found here http://polemicsreport.com/category/audio/podcast/
 Isaiah 55:11