1 the act or an instance of speculating; a theory or conjecture (made no speculation as to her age; is given to speculation).
2 a a speculative investment or enterprise (bought it as a speculation). b the practice of business speculating.
3 a game in which trump cards are bought or sold.
Etymology: ME f. OF speculation or LL speculatio (as SPECULATE)
Useful english dictionary. 2012.