adjective

not perfect; faulty or incomplete.

an imperfect grasp of English

faulty,flawed,defective,shoddy,unsound,unsaleable,unsellable,unfit,inferior,second-rate,below par,below standard,substandard,damaged,impaired,blemished,broken,cracked,torn,scratched,deformed,warped,shabby,inoperative,malfunctioning,not functioning,not working,out of order,in a state of disrepair,not up to snuff,not up to scratch,tenth-rate,crummy,lousy,duff,ropy,rubbish,not much cop,incomplete,abridged,not whole,not entire,partial,unfinished,half-done,deficient,lacking,wanting,unpolished,unrefined,patchy,rough,crude,disjointed,faltering,halting,hesitant,rudimentary,limited,non-fluent

noun

the imperfect tense.