jock itch

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. 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. Also called tinea cruris.

Wiktionary

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

WordNet 3.0

1. n. fungal infection of the groin (most common in men)