Meaning of "dot" in Essential American English Dictionary

dot

noun us /dɑt/

a small, round mark or spot:

a pattern of blue and green dots

B1 [ no plural ] the spoken form of “.” in an Internet address:

dot com (= .com)
on the dot

at that exact time:

We have to leave at 7:30 on the dot.

(Definition of “dot” from the Webster's Essential Mini Dictionary © Cambridge University Press)