strain at (one's) stool(redirected from strained at their stools)
strain at (one's) stool
To be constipated; to be unable or find it difficult to defecate. You mentioned that you've been straining at your stool lately. I'm going to prescribe a mild laxative for now, but you really ought to be eating more fruits, vegetables, and whole grains.
strain at stool
To have difficulty defecating.