Foul Play, Cowardly, Base
Noun and な adjective
ひれつ
卑劣な手段を使いやがって。
You played a mean trick!
If you treat someone in a lowly manner because you think they're inferior to you then you're a mean person. Plain and simple.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.