Meaning of “dot” - Learner’s Dictionary

dot

noun uk us /dɒt/
SPOT [ C ]

B2 a small, round mark or spot:

a pattern of blue and green dots
INTERNET [ U ] spoken

B1 the spoken form of '.' in an internet address:

dot co dot uk (= .co.uk)
on the dot

at that exact time:

We have to leave at 7.30 on the dot.

(Definition of “dot noun” from the Cambridge Learner’s Dictionary © Cambridge University Press)