1 (usu. foll. by in) incomplete; not having enough of a specified quality or ingredient.
2 insufficient in quantity, force, etc.
3 (in full mentally deficient) incapable of adequate social or intellectual behaviour through imperfect mental development.
Derivatives:
deficiently adv.
Etymology: L deficiens part. of deficere (as DEFECT)
Useful english dictionary. 2012.