n.
unsettled question
source of difficulty
1) to cause, create, pose, present a ~
2) to address, tackle; bring up, raise; resolve, settle, solve a ~
3) an acute, difficult, major, pressing, serious; insoluble, insurmountable ~
4) a complicated. involved, knotty, thorny ~
5) a delicate, ticklish ~
6) a minor, petty ~
7) an emotional; physical; psychological; social ~
8) a perennial ~
9) a ~ to + inf. (it's a ~ to make ends meet = it's a ~ making ends meet)
10) ( misc. ) the crux of a ~; to get to the heart of a ~
mathematical statement requiring a solution
11) to do, solve a ~
12) a complicated; difficult; easy; simple ~