conj. 1 a introducing the second of two alternatives (white or black). b introducing all but the first, or only the last, of any number of alternatives (white or grey or black; white, grey, or black). 2 (often prec. by either) introducing the only remaining possibility or choice given (take it or leave it; either come in or go out). 3 (prec. by whether) introducing the second part of an indirect question or conditional clause (ask him whether he was there or not; must go whether I like or dislike it). 4 introducing a synonym or explanation of a preceding word etc. (suffered from vertigo or giddiness). 5 introducing a significant afterthought (he must know - or is he bluffing?). 6 = or else (run or you'll be late). 7 poet. each of two; either (or in the heart or in the head). not A or B not A, and also not B. one or two (or two or three etc.) colloq. a few. or else 1 otherwise (do it now, or else you will have to do it tomorrow). 2 colloq. expressing a warning or threat (hand over the money or else). or rather introducing a rephrasing or qualification of a preceding statement etc. (he was there, or rather I heard that he was). or so (after a quantity or a number) or thereabouts (send me ten or so).
[ reduced form of obs. other conj. (which superseded OE oththe or), of uncert. orig. ]