This was a word used in a championship spelling bee, Most of the words were far tougher
than this one, which has been used here a half dozen times, but never defined.
I learned it a long time ago, in Kipling's The Elephant's Child.
"Then the Bi-Coloured-Python-Rock-Snake came down from the bank, and knotted himself
in a double-clove-hitch round the Elephant's Child's hind legs, and said, 'Rash and
inexperienced traveller, we will now seriously devote ourselves to a little high tension,
because if we do not, it is my impression that yonder self-propelling man-of-war with
the armour-plated upper deck' (and by this, O Best Beloved, he meant the Crocodile),
'will permanently vitiate your future career."

vitiate
vt.
< L vitiatus, pp. of vitiare, to vitiate < vitium, VICE16
1 to make imperfect, faulty, or impure; spoil; corrupt
2 to weaken morally; debase; pervert
3 to make (a contract, or other legal instrument) ineffective; invalidate
vitiation
.

n.