Call it what you want, but when you aren’t telling the truth — the whole truth, and nothing but the truth — then it’s lying.
Telling a date a half-truth now because it sounds better than the actual truth means that if the relationship progresses, the whole truth will eventually come out… and then your now boyfriend/girlfriend could be upset that you weren’t entirely honest from the get-go.
Omitting the truth is another form of lying. When the truth comes out, you will end up with more issues then you would if you just told the truth from date one. I’m not saying you have to be an open book and admit everything under the sun, but when the time comes to be clear on a topic, do so! Think about the repercussions before you decide how to answer — is it worth not being forthright?