(literally) Being seen or targeted, often through the sights of a weapon. / (figuratively) The target or object of one's efforts or ambitions. / (figuratively) Still achievable.

plural of one and only

(idiomatic) Unique, one of a kind.

(idiomatic) Only love, sole sweetheart.

plural of hole in one

Having only one hand. / Performed using only one hand. / Designed for use with one hand / (specifically, of reading or reading material) Pornographic in nature. / That uses one hand.

Using only one hand; one-handedly. / (figuratively) Very easily, without effort.

plural of number one

simple past tense and past participle of one-up

(slang) obsession with a particular person who is idealized as the only right one to date or to marry, often without any actual relationship developments.