also: オヤジか
noun, noun or participle which takes 'suru'
turning into an old man; becoming like a middle-aged guy
Colloquial, often self-deprecating or humorous. Describes a younger person (especially a man) starting to act, think, or look like a stereotypical middle-aged man (オヤジ).
最近、休みの日はゴロゴロしてばかりで、完全におやじ化してるな。
Lately I just laze around all day on my days off—I'm totally turning into an old man.
彼も30過ぎて、好みの音楽が演歌になって、おやじ化が進んでるよね。
He's past 30 now and his taste in music has shifted to enka—he's really becoming an old geezer.