Problem

n. difficulty, situation that requires a solution; question (on a test)

adj. troublesome, presenting a problem, presenting a difficulty

A problem is an obstacle which makes it difficult to achieve a desired goal, objective or purpose. It refers to a situation, condition, or issue that is yet unresolved. In a broad sense, a problem exists when an individual becomes aware of a significant difference between what actually is and what is desired. Every problem asks for an answer or solution.
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Problem a question to which there is no obvious, immediate answer; a question that requires some work done on it before a solution can be available. [more]Problem - Community and Resources

Noun
1. a state of difficulty that needs to be resolved; "she and her husband are having problems"; "it is always a job to contact him"; "urban problems such as traffic congestion and smog"
(synonym) job
(hypernym) difficulty
(hyponym) race problem
2. a source of difficulty; "one trouble after another delayed the job"; "what's the problem?"
(synonym) trouble
(hypernym) difficulty
(hyponym) can of worms
3. a question raised for consideration or solution; "our homework consisted of ten problems to solve"
(hypernym) question, head
(hyponym) puzzle, puzzler, mystifier, teaser

n. problem, riddle, puzzle, inconvenience, trouble, bother, difficulty, situation that requires a solution