(neurology, chiefly US) A genetic disorder caused by the presence of all or part of a third copy of chromosome 21 (a chromosomal excess), whereby the patients bear a certain resemblance to the Mongoloid race, such as a small head and tilted eyelids, and typically have a delay in cognitive ability and physical growth.

Used other than figuratively or idiomatically: see get, down. / (transitive or intransitive) To bring or come down; to descend; to cause to bring or come down. / (transitive) To concentrate; attend.

(nautical) Of a ship: so far distant that only the masts and sails are visible above the horizon.

(nautical) To close or make watertight, referring to hatches and cargo. / (transitive) To secure. / (intransitive) To prepare for adversity.

(intransitive, Britain) To become quieter. / (intransitive, Britain) To reduce intensity of an activity. / (transitive, Britain) To make someone or something become quieter.

Used other than figuratively or idiomatically: see bear, down. / (nautical) To steer away from the wind; to approach from windward. / (transitive) To push (someone) to the ground; to defeat, overcome.

(intransitive) To stop functioning. (machine, computer, vehicle) / (intransitive) To collapse, physically or in structure. (unexpectedly) / (intransitive) To demolish, to pull down. (intentionally)

Misspelling of breakdown.

(transitive) To hit or knock (something or someone), intentionally or accidentally, so that it falls. / (transitive) To demolish.

(idiomatic) To put forth the needed effort; to focus; become serious; apply oneself (e.g. to work or study).