Definitions for "Steric hindrance"
Slowing of the rate of a chemical reaction owing to the presence of structures on the reagents that mechanically interfere with the motions associated with the reaction, typically by obstructing the reaction site.
Physical hindrance to something.
Atoms in a molecule are forced into certain configurations because other parts of the molecule are occupying nearby regions in space and physically blocking certain atoms from exploring those regions.
A restriction on the reactivity of a group due to the spatical arrangements of neighboring groups.