Meaning of “log in/on” - Learner’s Dictionary

log in/on

phrasal verb with log us uk /lɒɡ/ verb [ T ] present participle logging, past tense and past participle logged

B2 to connect a computer to a system of computers by typing your name and often a password, usually so that you can start working

(Definition of “log in/on” from the Cambridge Learner’s Dictionary © Cambridge University Press)