spontaneous = "amorous"

[Jonathan Lighter]

Some pill said to turn geezer guys into unstoppable sex dynamos is currently running a TV commercial during which the geezer-guy actor says, "We were feeling spontaneous. Then we were...interrupted."
 
Broadly, this must mean "disposed to act on one's immediate emotional promptings."   But I bet the word mostly comes to mean "amorous" by the 23rd Century.
 
OED 1.b doesn't quite cover this usage.
 
JL




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