We left that issue pending.
The bill is still pending.
未決の問題がいくつか残っている。
Several undecided issues remain.
noun which may take the genitive case particle 'no', noun
unconvicted; awaiting judgment
Specifically refers to a person who has not yet been convicted or a case awaiting a court decision. Legal term.
Antonyms: 既決
未決囚として拘置所に収容されている。
He is being held in a detention center as an unconvicted prisoner.
事件は今も未決のままだ。
The case remains unresolved even now.
保留 implies a decision is deliberately being held back or postponed, whereas 未決 simply states that it has not yet been settled.
未決 is a more formal/legal term for something pending a decision (e.g. court cases), while 未解決 is broader and covers any unsolved problem, mystery, or issue.
unconvicted prisoner; prisoner awaiting trial
detention prison; remand prison
outstanding account; unsettled account
detention pending trial; pretrial detention
Compound of 未 (mi, 'not yet') and 決 (ketsu, 'decide'). The spelling and meaning are transparently derived from the kanji components.