(law) Any of various sexual deviations that, at one time or another, have been considered to be so unnatural as to be illegal.

(intransitive, idiomatic) To waste effort on a futile project.

Unequivocally and intransigently opposed to.

(idiomatic) To manipulate opponents or competitors in a manner which benefits the manipulator.

Alternative form of play both sides against the middle

(idiomatic) In a very difficult position.

(law, singular only) The rule that prevents a testator or other transferor of property from controlling further transfer of his property more than twenty-one years after the death of anyone alive at the time of the original transfer who may have some interest in the transfer.

plural of rule against perpetuities

(now rare) To be unfavourable to; to work against.

(idiomatic) Contrary to the flow of the game.