boast, boasts, boastful

Definition:

The term "boast" means to talk proudly about something or someone. Often it means to brag about oneself.

Someone who is "boastful" talks about himself in a proud way.
God rebuked the Israelites for "boasting in" their idols. They arrogantly worshiped false gods instead of the true God.
The Bible also talks about people boasting in such things as their wealth, their strength, their fruitful fields, and their laws. This means that they were proud about these things and did not acknowledge that God is the one who provided these things.
God urged the Israelites to instead "boast" or be proud about the fact that they know him.
The apostle Paul also talks about boasting in the Lord, which means being glad and thankful to God for all he has done for them.

Other ways to translate "boast" could include "brag" or "talk proudly" or "be proud."
The term "boastful" could be translated by a word or phrase that means "full of prideful talk" or "prideful" or "talking proudly about oneself."
In the context of boasting in or about knowing God, this could be translated as "take pride in" or "exalt in" or "be very glad about" or "give thanks to God about."
Some languages have two words for "pride": one that is negative, with the meaning of being arrogant, and the other that is positive, with the meaning of taking pride in one's work, family, or country.