All 3 Uses of

mock
in
To Kill a Mockingbird

He's not trying to mock you, he's trying to be polite.
p. 207.4 *

mock = make fun of

Uses with a meaning too rare to warrant foucs:

High above us in the darkness a solitary mocker poured out his repertoire in blissful unawareness of whose tree he sat in, plunging from the shrill kee, kee of the sunflower bird to the irascible qua-ack of a bluejay, to the sad lament of Poor Will, Poor Will, Poor Will.
p. 293.1 *

mocker = a mockingbird

Definitions:

(1) (mock as in: don't mock me)
make fun of (ridicule--sometimes by imitating in an exaggerated manner)

or (more rarely): just to make fun or to be ridiculous without targeting anyone as a victim

These senses of mockery come together when a comedian pokes fun at a politician by pretending to be the politician and saying ridiculous things.
(2) (mock as in: a mock trial)
not real
(3) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

Less commonly, mock can refer to a way of preparing food. Mockers can be an abbreviation for mockingbirds.