What is the meaning of the word "rack"?

Definitions:

A historical torture device used to stretch the body. NOUN
- Prisoners were interrogated on the rack in medieval times.
A structure for organizing or holding items. NOUN
- She hung her coat on the rack by the door.
Rib section of meat. NOUN
- He ordered a rack of ribs at the barbecue place.
The triangle used to position balls in billiards. NOUN
- He set up the balls using the rack.
To search or struggle mentally. VERB
- He racked his brain trying to remember the name.
To strain or stretch. VERB
- The illness racked his body with pain.
To torment or cause suffering. VERB
- She was racked with guilt over the decision.