(usually capitalized and preceded by the) The Kentucky Derby horse race.

(idiomatic) To experience the suffering or discipline necessary to bring one to a certain degree of knowledge or skill, or to a certain mental state.

Ceteris paribus.

(idiomatic) Something that may lead to gain, depending on the outcome; a position for which to campaign or cheer. / Used other than figuratively or idiomatically: see dog, hunt.

plural of blast from the past

(idiomatic, intensifier, simile) Unceasingly; very; thoroughly; to a very high degree.

(idiomatic) To insist on the total realization of a goal and reject any compromise, thereby decreasing the chance of achieving even a part of that goal.

(informal, humorous) Frightening imagined creatures; ghosts or other supernatural beings.

(espionage) Of a spy: to return home after having gone undercover in enemy territory. / (by extension) To gain widespread acceptance in a group or society, especially where there was not any before.

(attributive) spot the difference