Piggybacking

[Tina]

[The act] of joining [something] that [already] exists.

[Mary Mallozziberg]

present participle of piggyback

[Tariq Zaki]

When you [boof] using [someone elses] boof tool. (Generally [frowned upon])

[Tina]

[Taking advantage] of the roommate dish-washing routine.

When your roommate has not yet washed their pot or pan, and it is still [clean enough] to [swish] water in and cook your own meal. You then leave it where you found it so they can wash it.

Only legitimate if the roommate is unaware of your use.