jock itch

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A fungal infection of the skin of the groin area, occurring more commonly in warm weather and among males and characterized by red ringlike areas, sometimes with small blisters, and severe itching; ringworm of the groin.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun a fungal infection, tinea cruris, of the groin region, due to the fungus Trichophyton rubrum and others.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun fungal infection of the groin (most common in men)