Imprecise means not clear and not exact. A number can be imprecise if you say “about fifty” when someone needed 47. A sentence can be imprecise if the listener cannot tell what you really meant. It is often a gentle fault: the idea may still be in the right area, just not sharp. Inaccurate is stronger — that one is wrong. Scientists, teachers, and editors use precise and imprecise a lot. In daily talk we often say vague for words and rough for numbers, and keep imprecise for slightly more careful speech. Though actually, people also stretch it: “imprecise language” can mean the speaker is hiding something, not only that they lack a better word.