something that is objectively meaningless according to the person telling you this phrase but meaningful (and relevant) to everyone else you know (the 'everyone you know' includes most people in your generation/age range/social category)
boy 1) my mother says that smoking Mary Jane is meaningless
boy 2) just ignore your old lady. her opinion is subjectively meaningless but meaningful to idiotager or idiotagers in our class.
To have sex with someone you don't have feelings for or don't really like...just to have sex for pleasure but not because you love them to actually make love to them