cutthroat

noun

1. (countable, uncountable)A murderer who slits the throats of victims.
2. (countable, uncountable)An unscrupulous, ruthless or unethical person.

   “The jail had not housed a white criminal in over four years, and there is seldom a prisoner of any kind, the Sheriff being a lazy no-good, prone to take his ease with a bottle of liquor, and let trouble-makers and thieves, even the most dangerous type of cutthroats, run free and wild.”

3. (uncountable)A three-player pocket billiards game where the object is to be the last player with at least one ball still on the table.
4. (abbreviation, alt-of, countable, ellipsis, uncountable)Ellipsis of cutthroat compound (“an agentive-instrumental verb-noun compound word”).

   “Children go through a phase of compound acquisition in which they invent cutthroats spontaneously before dropping the habit again.”

adj

1. Involving the cutting of throats.
2. Of or relating to a card game where everyone plays for him or herself rather than playing with a partner.

   “He found that playing cutthroat Spades was much more difficult than playing with a partner.”

3. Ruthlessly competitive, dog-eat-dog.

   “Law is a cutthroat business, you always have to look out to see who is trying to outdo you.”

   “More specifically, Scrabblers are diehard, competitive, and occasionally cutthroat players who treat the game like it's chess or baseball...”

   “While these esports are often framed as battles of mental strategies and mechanical skills, how players juggle their hundreds, or thousands, of simultaneously ticking clocks and timers defines their ability to succeed in cutthroat competitions.”