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Webster 1913 Edition

(līf′mātˊ)

Noun.

Companion for life.

Hawthorne.

lifemate ‎(plural lifemates)

A companion for life.
- 1850, Nathaniel Hawthorne, The Scarlet Letter, Introduction:
  The truth seems to be, however, that when he casts his leaves forth upon the wind, the author addresses, not the many who will fling aside his volume, or never take it up, but the few who will understand him better than most of his schoolmates or lifemates.