In botany, trunk refers to the main structural member of a tree that is supported by and directly attached to the roots and which in turn supports the branches. The trunk is also often called the bole. The trunk is covered by the bark, which is an important diagnostic feature in tree identification, and which often differs markedly from the bottom of the trunk to the top, depending on the species. The trunk, or bole, is the most important part of the tree for timber production. Also see log.

The trunk or torso of the human body is the body without the head, arms and legs.

In American English, the trunk of a car is a compartment used for storage space, usually placed at the car's rear.

In telecommunication, the term trunk has the following meanings:

1. In a communications network, a single transmission channel between two points that are switching centers or nodes, or both.

2. [A] circuit between switchboards or other switching equipment, as distinguished from circuits which extend between central office switching equipment and information origination/termination equipment.

Note: Trunks may be used to interconnect switches, such as major, minor, public and private switches, to form networks.

Source: from Federal Standard 1037C and from MIL-STD-188 and from the Code of Federal Regulations, Telecommunications Parts 0-199