stern

nouns

the rear part of a ship
after part, poop, quarter, stern, tail
the fleshy part of the human body that you sit on
"he deserves a good kick in the butt"; "are you going to sit on your fanny and do nothing?"
arse, ass, backside, behind, bottom, bum, buns, butt, buttocks, can, derriere, fanny, fundament, hind end, hindquarters, keister, nates, posterior, prat, rear, rear end, rump, seat, stern, tail, tail end, tooshie, tush

adjectives

of a stern or strict bearing or demeanor; forbidding in aspect
"an austere expression"; "a stern face"
austere, stern
not to be placated or appeased or moved by entreaty
"grim determination"; "grim necessity"; "Russia's final hour, it seemed, approached with inexorable certainty"; "relentless persecution"; "the stern demands of parenthood"
grim, inexorable, relentless, stern, unappeasable, unforgiving, unrelenting
is derived from
sternness
severe and unremitting in making demands
"an exacting instructor"; "a stern disciplinarian"; "strict standards"
exacting, stern, strict
is derived from
sternness
severely simple
"a stark interior"
austere, severe, stark, stern
is derived from
sternness