(anatomy) One of the areas of the sarcoplasmic reticulum of striated muscle cells, surrounding T tubules, that are able to store calcium and release it when an action potential courses down the T t...

present participle of clue

(chiefly dialectal) Being from without; strange; foreign; peculiar.

(gambling) In roulette, the call made by the croupier as the wheel is set in motion. / (idiomatic) Things have reached an irreversible point; you cannot go back now that you have done something.