Other forms: timidest; timider
Timid means "overly cautious or fearful," like a timid driver who drives very slowly or avoids highways altogether.
Timid comes from the Middle French word timide, meaning "easily frightened, shy." Those who are timid often worry that things will go wrong: a timid eater orders bland food to avoid the possibility not liking the flavor of something new, just as a timid partygoer talks to people he already knows, afraid that he won't be able to talk to strangers.