Main entry: uncertain, unsure, incertain
Definition: lacking or indicating lack of confidence or assurance
Usage: uncertain of his convictions; unsure of himself and his future; moving with uncertain (or unsure) steps; an uncertain smile; touched the ornaments with uncertain fingers
Main entry: shy, timid, unsure, diffident
Definition: lacking self-confidence
Usage: stood in the doorway diffident and abashed; problems that call for bold not timid responses; a very unsure young man
Antonyms: confident
Definition: having or marked by confidence or assurance