An affectionate term used commonly by military people.
When male human ejaculate is mixed with water many of the insoluble lipids, proteins, and long chain carbohydrates are clumped together forming stringy jellyfish like white clumps. They are commonly seen in and around public and communal showers, such as dorm bathrooms or military showers because many people tend to use this as their "private time" and masturbate in the shower.

Since they are so often found in military showers and bathrooms they have been dubbed "battle jellies."
"Dude stop jerking in the damn shower! I stepped on your fucking battle jelly yesterday."
by roflcockter January 28, 2017
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