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 particularly difficult question or puzzle.
Someone who, or something which, poses; a person who sets their body in a fixed position, such as for photography or painting.
A poseur; someone who affects some behaviour, style, attitude or other condition, often to impress or influence others.
Someone who asks a question or sets a problem.