An effeminate (often homosexual) man.

From the habit of certain women riding a horse not by straddling it, but by riding side-on with legs to one side, in order not to break the bottle neck. Hence, to ride side-saddle, i.e. to be effeminate.
Man: Craig hasn't ever had a girlfriend. I reckon he must be a side-saddler.
Another man: Haven't you heard? He's been riding side-saddle since he was seventeen.
by Tama Boyle January 31, 2007
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