I. ˈ ̷ ̷ˌ ̷ ̷ noun
Etymology: light (IV) + weight
1. : one of less than average weight: as
a. : a boxer weighing more than 126 but not over 135 pounds
b. : a wrestler weighing more than 134 but not over 145 pounds
2.
a. : a person lacking in strength of character or intellectual depth
shows up its author as a lightweight — C.J.Rolo
if she hadn't been the lightweight , the weakling she was — Donn Byrne
b. : a person inadequately qualified for the position he fills or the duties he is charged with
the muddled thinking of a lightweight in diplomacy — Times Literary Supplement
II. adjective
1. : of or relating to a lightweight
a lightweight bout
the lightweight championship
2. : having less than average weight without fully corresponding lessening of strength, warmth, or other desirable quality
lightweight aluminum railroad cars
a lightweight sweater
3. : lacking in earnestness or profundity : not to be taken seriously
a lightweight kid who gets by on bare maintenance mentality — Mademoiselle
lightweight discourses on long dead and justly forgotten court ladies — Saturday Review