Older Graduate, Superior
Noun
せんぱい
俺の先輩、悪い人では無いんだけどさ、ただちょっと俺とは反りが合わないんだよね。
My superior isn’t a bad guy, but he and I just haven’t been able to hit it off.
My comrade who came before me is my senior, my senpai (せんぱい).
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.