What is the meaning of Side_chain?

That part of a molecule attached to some core structure; a radical.

Any of the variable parts of amino acids that extend from the peptide backbone in proteins; they are referred to as R-groups, which branch off the backbone at the alpha carbon (Cα).

Auxiliary audio input fed to a synthesizer etc. and used to selectively trigger an effect.

A separate blockchain attached to a parent blockchain (mainchain) to extend its functionalities.

On some railways, a chain fitted on both sides of a centre coupler or buffer at each end of a rail vehicle, which has a hook for connection to a corresponding chain on the next vehicle in a train.

To use auxiliary audio input in that manner.

Source: wiktionary.org