Real Dictionary

tower
countable noun: A tower is a tall box that contains the main parts of a computer, such as the hard disk and the drives.
countable noun: A tower is a tall structure that is used for sending radio or television signals.
countable noun: A tower is a tall, narrow building, that either stands alone or forms part of another building such as a church or castle.
countable noun: A tower is the same as a tower block.
verb: Someone or something that towers over surrounding people or things is a lot taller than they are.

tower in American English 1
a building or structure that is relatively high for its length and width, either standing alone or forming part of another building
to rise high or stand high like a tower
noun: a building or structure high in proportion to its lateral dimensions, either isolated or forming part of a building

tower in American English 2
noun: a person or thing that tows

tower in British English
noun: a tall, usually square or circular structure, sometimes part of a larger building and usually built for a specific purpose