For instance, you are actively on dating apps while in a committed relationship; creating/seeking romantic opportunities outside of your partner/spouse.
Adjective applied to a student who tries to get out of a summer homework assignment by "thinking" it was optional.
It rarely works but might get you permission to hand the assignment in late.
Teacher, "Where is your summer book report?"
Student, "Uhh... I thought that was optional."
Teacher, "How optionalistic of you."