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2.
Skin irrated from ejaculation
scabs of dry skin where ejaculation was shot on skin.

"Yo I ejaculated on some fine ass bitches face and now shes got cumrash."
by THCisDANK May 02, 2007
 
1.
The mark (redness) left after you cum and wipe it off.
I jizzed on your mum's face last night and left her with a cum rash.
by Surox May 16, 2009