n. & v.
n. 1 a destroyed or wrecked state. 2 a person's or thing's downfall or elimination (the ruin of my hopes). 3 a the complete loss of one's property or position (bring to ruin). b a person who has suffered ruin. 4 (in sing. or pl.) the remains of a building etc. that has suffered ruin (an old ruin; ancient ruins). 5 a cause of ruin (will be the ruin of us).
v. 1 tr. a bring to ruin (your extravagance has ruined me). b utterly impair or wreck (the rain ruined my hat). 2 tr. (esp. as ruined adj.) reduce to ruins. 3 intr. poet. fall headlong or with a crash. in ruins 1 in a state of ruin. 2 completely wrecked (their hopes were in ruins).
[ ME f. OF ruine f. L ruina f. ruere fall ]