i-adjective
like an old man; doddering; seedy
Describes a person, appearance, or manner that is unkempt, shabby, or reminiscent of an old man; often mildly derogatory.
彼はまだ若いのに、服装がじじむさい。
He's still young, but his clothes make him look like an old man.
そのじじむさい帽子
You'd better stop wearing that seedy hat.