Nonpolar Bond
Definition
A covalent bond where electrons are shared equally, or nearly so: neither atom hogs the electrons.
Technical definition
A nonpolar covalent bond forms between atoms with little or no electronegativity difference (typically below 0.4), so shared electrons are distributed symmetrically and no significant partial charges develop.
Example
The H-H bond in hydrogen gas and the C-H bonds in methane are nonpolar: the electrons are shared evenly.
Common confusion
Nonpolar bonds can exist inside polar molecules. What matters for the molecule's overall polarity is the combination of bond polarity and molecular shape.