lightweight

adjective

1. light in weight.
2. being lighter in weight, texture, etc., than another item or object of identical use, quality, or function: a lightweight topcoat; a lightweight alloy for ship construction.
3. without seriousness of purpose; trivial or trifling: lightweight reading.
4. of or relating to a lightweight: He’s the new lightweight contender.
5. (of a horse, especially a hunter) able to carry up to 165 pounds (75 kg).

noun

6. a person of less than average weight.
7. Informal. a person who is of little influence, importance, or effect.
8. a boxer or other contestant intermediate in weight between a featherweight and a welterweight, especially a professional boxer weighing between 126 and 135 pounds (56.7–61 kg).

adjective

1. of a relatively light weight
2. not serious; trivial

noun

3. a person or animal of a relatively light weight
4. 1. a professional boxer weighing 130–135 pounds (59–61 kg)
   2. an amateur boxer weighing 57–60 kg (126–132 pounds)
   3. (as modifier)the lightweight contender
5. a wrestler in a similar weight category (usually 115–126 pounds (52–57 kg))
6. informal a person of little importance or influence

adj.also light-weight, 1773 in horse-racing, also in pugilism; from light (adj.1) + weight. Figurative sense of “inconsequential” first attested 1809.