Knockout

In Granny, a knockout is when the Player gets knocked unconscious and sent to the next day. Knockouts can also cause a Game Over if the Player is on the fifth day (or sixth day, if the painting has been completed). There are also five ways for Granny to get knocked out, listed below, which will leave her unconscious for a short duration (time of which depends on the method and Difficulty Level).

Player

As of Version 1.8, there are seven ways the Player can be knocked out.

Getting caught by Granny.
Falling from a large height.
Getting bitten by the Spider.
Getting blown up by an explosion from the Gasoline Can.
Getting eaten by Spider Mom.
Getting blown up by choosing the wrong chest.
Glitches occur when interacting/joshing around with either the Floor Lamp, the Chair, the Cardboard Boxes, the table or Granny's knocked out body.

Granny

Granny can also be knocked out by the Player through various methods. She will respawn after a short period of time, with the time period being dictated by the difficulty and the method of knockout. There are seven ways Granny can die, along with a table for timers listed below:

Getting shot by a Crossbow with a Tranquilizer Dart. (Grants a short timer)
Getting hit by a Shotgun blast. (Grants a long timer)
Getting locked in the active Sauna for 15 seconds. (Grants a short timer)
Getting caught in the Gasoline Can explosion. (Grants a long timer)
Getting hit by the Car. (Grants a short timer)
Frozen by Freeze Trap. (Grants a short timer)

Granny respawns after a certain period of time, although the timers are dictated by both the difficulty and what she was killed by.

Timers	Easy	Normal	Hard	Extreme
Short Timer	2 Minutes	1 Minute	30 Seconds	15 Seconds
Long Timer	2 Minutes and 30 Seconds	1 Minute and 30 Seconds	1 Minute	30 Seconds

Trivia

For some reason, Granny's timer is not a long one when frozen or getting hit by a car, despite supposedly sustaining much more damage to herself than even a shotgun shot.
It is unknown why Granny always puts the Player back in the Starting Bedroom after the Player gets knocked out.
If the Player gets knocked out by the Gasoline Can's explosion, they will sometimes fall through to the floor below, which is followed by the black screen when knocked out, e.g. if shot in the Starting Bedroom they will fall to the Dining Room.
Sometimes, even if Granny sees you hide under a bed or inside the car, she will not knock you out. Instead, she will just stand there and walk away after a few moments. This seems to happen at complete random, probably meaning it's a bug or oversight in her AI. A video of this can be seen here
In V1.8, there's a glitch where if you fall from the Unstable Flooring you somehow won't get killed. Instead, a Fall Damage will happen.