1. (adjetive) characterized by a lightly pert and exuberant quality (impertinent, irreverent, pert, saucy)
2. (adjetive) not pertinent to the matter under consideration (extraneous, immaterial, impertinent, orthogonal)
"Mentioned several impertinent facts before finally coming to the point"
3. (adjetive) improperly forward or bold (fresh, impertinent, impudent, overbold, smart, saucy, sassy, wise)
"Impertinent of a child to lecture a grownup"