Refers to Women Marines, once officially known as WMs. Use this expression with a great deal of caution around female marines or you will wind up with a fat lip faster than you dreamed possible.
*runs into wall*
*is scared to go outside*
Chelz: *wonders where cris and brookie went*
Cris: *wonders why chelz is wondering where she is when she's right here*
Brookie: *ran away*