The
perceived
gender of something or someone, especially in the
absence of proof one way or another. It varies wildly from
place to place,
person to person, and
thing to thing, sometimes with no obvious correlation to
logic.
For example, where I'm from boats and airplanes are assumed to be female. So are flags. Some curious folks give their firearms female names. I'm sure there are different conventions in other societies.
It can get stranger. You know those drawings of smiley faces? A circle with two dots for eyes and a curve for a mouth? The ones that a colon followed by a right-parenthesis (:)) are meant to represent? Those are male by default. You have to add something to them, like full lips, long eyelashes or hair, a bow, or some other marker of femininity, to imply that it is supposed to be female. The same applies to other types of cartoons, like stick figures. Without some extra lines to indicate a skirt, hair, breasts or something, they all wind up being male. Graphically, the only thing that keeps Minnie Mouse and Daisy Duck from being Mickey Mouse and Donald Duck are their lipstick and accessories.
Of course, it also varies from person to person. It always seemed to me that dogs, full size pick-up trucks, those big old ENIAC-style computers, mountains and outdoor grills would primarily be male. While cats, sports coupes, churches (the buildings, not the institutions), farms, stoves and washing machines would be female.
I'm sure that most of this has to do with associatiating items with their users.
As far as societal constructs go, this is one of those omnipresent but rarely observed ones. At least until you start looking for it, then you can't turn around with seeing it.