To be economical with the truth literally means to avoid revealing too much of the truth. While the idea may have an approbatory sense of prudence or diplomacy, the phrase is often either used euphemistically to denote dissimulation ( misleading by withholding pertinent information) or else used ironically to mean outright lying .

The phrase 'Economical with the truth' - meaning and origin. What's the meaning of the phrase 'Economical with the truth'? Conveying an untrue version of events by leaving out the important facts. A euphemism for lying, in short.