adv. 25B6; adverb
he walked quickly : FAST, swiftly, briskly, rapidly, speedily, at the speed of light, at full tilt, as fast as one's legs can carry one, at a gallop, at the double, post-haste, hotfoot; informal double quick, p.d.q. (pretty damn quick), like (greased) lightning, hell for leather, like mad, like blazes, like the wind; Brit. informal like the clappers, like billy-o; N. Amer. informal lickety-split; poetic/literary apace.
you'd better leave quickly : IMMEDIATELY, directly, at once, now, straight away, right away, instantly, forthwith, without delay, without further ado; soon, promptly, early; N. Amer. momentarily; informal like a shot, a.s.a.p. (as soon as possible), pronto, before you can say Jack Robinson, straight off.
he quickly inspected it : BRIEFLY, fleetingly, briskly; hastily, hurriedly, cursorily, perfunctorily, superficially, desultorily.