Definition of tare:
(n) :
a
vetch, or the seed of a vetch; a damaging weed growing in fields of grain (with reference to Matthew 13:25: "But while men slept, his enemy came and sowed tares among the wheat, and went his way." The King James Version (Authorized))
"1985, I saw as I thought an uncle and guardian who has led a sober, industrious and Christian life and finds himself obliged to look on the tares of folly in his own close kin. -- John Fowles, A Maggot"
(v) :
to allow for the tare; to set a counter or meter to a valid
zero (usually
weight) value, discounting the weight of the empty container