Lying by omission
Also known as a continuing misrepresentation, a lie by omission occurs when an important fact is left out in order to foster a misconception. Lying by omission includes failures to correct pre-existing misconceptions. When the seller of a car declares it has been serviced regularly but does not tell that a fault was reported at the last service, the seller lies by omission.
By that definition, it would appear that you would have to say "something", but leave out important details. Not saying anything at all, doesn't constitute a lie IMHO.