S: (n) difficulty (a factor causing trouble in achieving a positive result or tending to produce a negative result) "serious difficulties were encountered in obtaining a pure reagent"
S: (n) trouble, problem (a source of difficulty) "one trouble after another delayed the job"; "what's the problem?"
S: (n) facer ((a dated Briticism) a serious difficulty with which one is suddenly faced)
S: (n) killer (a difficulty that is hard to deal with) "that exam was a real killer"
S: (n) kink (a difficulty or flaw in a plan or operation) "there are still a few kinks to iron out"