Dictionary definition · sub
noun
- a large sandwich made of a long crusty roll split lengthwise and filled with meats and cheese (and tomato and onion and lettuce and condiments); different names are used in different sections of the United States
- a submersible warship usually armed with torpedoes
verb
- be a substitute"The young teacher had to substitute for the sick colleague"
Source: Open English WordNet (CC BY 4.0).