(verb) When one parties soft, they do not party hard, i.e they do not party at all, as it is impossible to party softly. If one were to party softly, one would be partying in an event akin to a tea party or seminar with an English lecturer.
Bouncer : "Oi, you look to young to be in here, you might party soft"
Man 2: "Mate, here's my fake i.d, don't read it, its pants, but I guarantee you, I'm here to party so hard"
(1) The pliant, moist, intimate womanhood located between the thighs that begs for the tender caresses of an understanding hand, a wet tongue, or the bold insertion of a stiff cock.
(2) Genitals, female and male, generally.
(1) Jenny has such a crush on Adam; you can tell she wants him to caress her soft parts.
(2) Jenny and Adam rubbed each others' soft parts.