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

Source: The Collaborative International Dictionary of English v.0.48
 

log in v : enter a computer; "Have you logged in lately?" [syn: log on, log-in] [ant: log out]

Source: WordNet (r) 2.0