It's an alternative phrase for "That sucks".
Leeches suck so if something is a leech, then it sucks.
B. 5/31/17
Leeches suck so if something is a leech, then it sucks.
B. 5/31/17
1. Friend: Man I just failed my final
You: Dang that's a leech
2. Friend: *sings terribly*
You: Stop man, you're a leech at singing
You: Dang that's a leech
2. Friend: *sings terribly*
You: Stop man, you're a leech at singing
by Nicemanberries May 31, 2017