Pronounced toe-back. To be extremely ugly, either naturally (upon birth), unnaturally (some crazy deforming accident) or through surgical modification (plastic surgery which made your face worse instead of helping).

ugly horrible nasty deformed yuck dog

A term used to reference cannabis/marijuana/weed.

To back can be just defined as to support.
But it can also be slang for pulling out some kind of weaponery like a knife,

this is mostly used by people in Gangs or people involved in the streets.