From WordNet (r) 2.0 (August 2003) [wn]:
foe
n 1: an armed adversary (especially a member of an opposing
military force); "a soldier must be prepared to kill his
enemies" [syn: enemy, foeman, opposition]
2: a personal enemy; "they had been political foes for years"
[syn: enemy] [ant: ally]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Foe \Foe\ (f[=o]), n. [OE. fo, fa, AS. f[=a]h hostile; prob.
akin to E. fiend. [root]81. See Fiend, and cf. Feud a
quarrel.]
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1. One who entertains personal enmity, hatred, grudge, or
malice, against another; an enemy.
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A man's foes shall be they of his own household.
--Matt. x. 36
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2. An enemy in war; a hostile army.
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3. One who opposes on principle; an opponent; an adversary;
an ill-wisher; as, a foe to religion.
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A foe to received doctrines. --I. Watts
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From The Collaborative International Dictionary of English v.0.48 [gcide]:
Foe \Foe\, v. t.
To treat as an enemy. [Obs.] --Spenser.
[1913 Webster]