na-adjective, noun
Describes a person, situation, or thing that seems untrustworthy or not quite right. Often used in the phrase うろんな目つき (suspicious look).
あの男はどうもうろんな感じがする。
That man gives off a suspicious vibe.
彼女はうろんな目つきで私を見た。
She looked at me with a suspicious look.
怪しい is a more common and broader word for 'suspicious', 'dubious', or 'shady'. うろん is less frequent and has a slightly literary or old-fashioned feel.
The origin is uncertain. The kanji 胡乱 are ateji (characters used for their sound rather than meaning) and do not contribute to the word's meaning.