underpowered

under- +‎ powered

underpowered

1. simple past tense and past participle of underpower

underpowered (comparative more underpowered, superlative most underpowered)

1. Having insufficient power for its operation.
   • 1925, Stewart Edward White, New York: Grosset & Dunlap, Chapter 2,

     […] occasionally a flap-skitter duck, making up his mind to go a-visiting, gave himself over to the serious business of flight. Flap-flap-flap, skitter, skitter, skitter, went he, taxi-ing along like an underpowered airplane, leaving behind him incredible churnings of wake.

   • 1945, Neville Shute, New York: William Morrow & Co., Chapter 4, p. 111,

     The old under-powered van ground its way very noisily and rather slowly up the long steep hill out of the town.

• overpowered, OP