A problem that is challenging to solve.
Used other than figuratively or idiomatically: see hard, nut, crack.
A situation, person, group, etc. which is difficult to overcome or deal with.
A place, opportunity, etc. to which it is difficult to gain entry.
An amount that is difficult to finance.
A difficulty, problem, condition, or action contributing to such a situation.
A fault or interruption in a stratum.
A malfunction.
A violent occurrence or event.
Efforts taken or expended, typically beyond the normal required.
Liability to punishment; conflict with authority.
Wife. Clipping of trouble and strife.
A distressing or dangerous situation.
In weaker sense: to bother or inconvenience.
To mentally distress; to cause (someone) to be anxious or perplexed.
To worry; to be anxious.
To take pains to do something.