'log on' definitions:

Definition of 'log on'

From: WordNet
verb
Enter a computer; "Have you logged in lately?" [syn: log in, log on, log-in] [ant: log off, log out]

Definition of 'log on'

From: GCIDE
  • log in \log in\, log on \log on\, v. i. (Computers) To establish communication with a host computer from a terminal or remote computer. [PJC] Logistic