Definition of cutthroat:
(n) :
a
murderer who
slits the
throats of his victims; an unscrupulous, ruthless or unethical person
(adj) :
involving the
cutting of
throats; of or relating to a
card game where ever man plays for himself rather than playing with a partner
"he found that playing cutthroat Spades was much more difficult than playing with a partner."