What word could describe the movement of a parked car inside which a couple is making out?
"The car moved up and down", seems too simple. Maybe "sway", but it seems soft to me.
Solution 1:
A slightly quirky term for a car rocking up and down is jounce. Oxford English Dictionary, with two vehicle-appropriate examples:
- intransitive. To move violently up and down, to fall heavily against something; to bump, bounce, jolt; to go along with a heavy jolting pace.
1967 C. O. Skinner Madame Sarah (new ed.) viii. 171 The train..swayed, rocked, jounced and hustled a couple of passengers from their seats.
1971 D. E. Westlake I gave at Office (1972) 55 The two trucks jouncing off along the narrow dirt road through the swamp
Jouncing is rough. Often, jouncing is caused by the motion of the vehicle against rougher roads, as the second half of the definition ("to go along...") and most examples show.
Aggie gave a nod and watched the moped jounce down the country road toward town. (Connie Spittler, The Erotica Book Club for Nice Ladies, 2015)
However, motion within the car can also cause it to jounce:
He moaned again and tried to move. "Jane?" The car jounced with his movement and Jane felt her heart turn over with fear. (Amber Dean, Deadly Contact, 1963)