Other forms: meeker; meekest
The adjective meek describes a person who is willing to go along with whatever other people want to do, like a meek classmate who won't speak up, even when he or she is treated unfairly.
A meek person can also be humble, but these words aren't quite synonyms. If you are humble, you don't want a lot of attention, like the humble athlete who has a truly excellent performance yet after the game, tells reporters that it was group effort by the whole team. A meek person, on the other hand, would never think a reporter would ever want to talk to him or her, and if asked, would probably try to get someone else, someone more "worthy," to do it.