Definitions by Prince of Pugatory

another mule is kicking in your stall

Adultery:
Your significant other is having sex with someone else.

In Muddy Waters "Long Distant Call" or in Koko Taylor "Evil" The line Another Mule is Kicking in Your Stall refers to being cheated on.

another mule is kicking in your stall by Prince of Pugatory October 21, 2011