Swindler
You know that 詐欺 is "fraud." An expert at fraud (詐欺) is someone who does this a lot and possibly for a living. A swindler, some would say.
さぎし
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own. Will help to know the reading of 詐欺 as well.
「ねぇ、今俺のこと、嘘つきって言った？」「そうは言ってないけど、詐欺師とは言ったよ。」「はぁ？何言ってんだよ。マジ、信じらんねぇ。」
"Hey, did you just call me a liar?" "No, but I called you a crook." "Huh? What are you talking about!? I seriously can’t believe you."