1.  bm(n = noun.substance) dejection, faecal matter, faeces, fecal matter, feces, ordure, stool - solid excretory product evacuated from the bowels;
is a kind of body waste, excrement, excreta, excretion, excretory product
has particulars: dog do, dog shit, dog turd, doggy do, crap, dirt, poop, shit, shite, turd, droppings, dung, muck, meconium, melaena, melena

2.  bm(n = noun.process) bowel movement, movement - a euphemism for defecation; "he had a bowel movement"
is a kind of defecation, laxation, shitting

   an abbreviation for bowel movement; -- used as an informal euphemism, especially in hospitals. [PJC]

bm, abbr.
1 British Museum.
2 Bachelor of Medicine.