Flunked rhymes with:
plunked, spelunked, debunked, defunct, dunked, junked, plunked, spelunked, adjunct, banked, bengt, blanked, blinked, cranked, debunked, defunct, distinct, dunked, extinct, flanked, franked, hoodwinked, indistinct, instinct, interlinked, junked, linked, outflanked, plunked, precinct, ranked, sacrosanct, spanked, spelunked, succinct, tanked, thanked, winked, yanked
Flunked sounds like:
flanked, flimsiest, flinched, flummoxed