duct-n; 3 Senses

Sense Number 1: an enclosed man-made passage that conducts a substance such as air, water

Commentary: DUCT[+structure][+conduit][+tube][-animate][+passage][+substance][+air/+water/+electricity]

The air ducts in that building did not pass the building codes inspection.
John sealed his windows with duct tape. (tape for securing duct work together)
These metal ducts carry water around the machinery to cool it.

WordNet 3.0 Sense Numbers: 3

Sense Number 2: a vessel in a living being that conducts fluids, e.g., lymph, tears, sap

Commentary: DUCT[+structure][+conduit][+tube][+animate][+vessel][+fluid][+lymph/+bile/+sap/+tears]

This disease chokes off the tree's ducts so that sap cannot flow through it.
Chewing food stimulates the salivary ducts in the mouth.
The cancer had apparently spread via the lymphatic ducts in his armpits.
The bile duct passes bile from the liver or gallbladder to the duodenum.

WordNet 3.0 Sense Numbers: 1, 2

Sense Number 3: unusual environmental condition that restricts the path of radio or acoustic waves

Commentary: DUCT[+structure][+conduit][+layer][+environmental][+propagation][+wave][+radio/+acoustic/+microwave]
NOTE: can be present in atmosphere or ocean

Radio waves tend to follow the curvature of the earth within an atmospheric duct.
The study compares four evaporation duct models of the oceans.

WordNet 0.0 Sense Numbers: 4