This is an expression used to denote something that is irrelevant, useless or unfit for purpose. If you wanted to say someone was stupid, you could say “Her head is as empty as a eunuch’s ball sack.” If you wanted to say someone was useless, “He’s as much use as a eunuch’s ball sack.” Cowardly “If courage was balls you’d be a eunuch’s ball sack.” The expression is versatile and can be adapted to a wide variety of purposes.
A spousal eunuch is virtually identical to the 'spousal unit', but without the sex. Unlike ordinary eunuchs, spousal eunuchs usually have existing and potentially functional genitalia, but have stopped fucking their significant other for reasons which do not pertain to physical endowment.
I've been banging this married chick because her spousal eunuch can't get a boner without first being subjected to sexual domination. How refreshing it must be for her to get laid by a dude who doesn't have a ball gag lodged in his cake hole!
The most beautiful, amazing Haitian that you will ever meet. Kind, sociable and likes purple. She's the one that just gets into your heart and will stay there even if you don't see her again.