soil (one's) nappy(redirected from soils their nappies)
soil (one's) nappy
To defecate into the nappy (diaper) one is wearing. Primarily heard in UK. Uh oh, I think Tommy just soiled his nappy. I'd better go change it. I just hope I don't live so long that I end up in some nursing home soiling my nappy.
See also: soil