Plain English Meaning

A spin where the top of the object turns backward relative to how it's moving. As it travels through the air, this kind of spin pushes the object downward instead of lifting it up.

Full Definition

Rotation of an object such that its top surface moves opposite to the direction of travel through the air, causing air to be deflected downward over the top and creating a downward (negative) lift force via the Magnus effect.

Context Anchor

Seen in the Lift chapter when explaining the Magnus effect and how a spinning object can produce a lifting force.

Derivation

Plain compound of 'back' and 'spin' — the top surface spins backward against the direction the object is moving. Useful because the name itself describes the motion: top going back, air being thrown up and over, object pushed down.