When two cars are both going the same speed in different lanes making it impossible to pass them

In video-games, this term is used to describe two or more players who move together rather then going alone. In first person shooter games these people always travel together in hopes of taking out lone targets. In RPG it is used mostly in pvp and pk when two people attack one person to avoid dying.

any form of having sex

Hand holding, when done correctly entails but is not limited to=
Hot, sweaty fun filled sex.

Euphemism for masturbation, especially in a semi-secluded public area - for example in a cinema seat.

When the man shoves his whole hand up a girls ass and shakes the ovaries like a hand shake.

Euphemism for masturbation, especially when done in a secluded public place - for example a cinema seat.