runt

Concise Oxford English Dictionary © 2008 Oxford University Press:
runt/rʌnt/

▶noun

• 1 a small pig or other animal, especially the smallest in a litter.

  ■ derogatory an undersized or weak person.

• 2 a pigeon of a large domestic breed.

– derivatives
runty adjective.

– origin C16 (in the sense ‘old or decayed tree stump’): of unknown origin.