A “Bull Dyke” is a masculine lesbian who does not go in for overt signs of femininity.
Imagine a large, tattooed rigger, but only in female.
Bull Dykes usually sport crew cuts and wear masculine clothing such as lumber jack shirts or overalls.
Bull Dykes are normally the dominant partner in a lesbian relationship and are also known as “Diesel Dykes”.
“That Bull Dyke made a move on my mate, it put the frighteners on her!”.