noun. 1  the period of time during which a person is under the influence of LSD. 2  I was on an eight-hour trip yesterday. 3  See more words with the same meaning: a period of time. Or someone who ACTS like they are on a hallucinogenic drug that causes them to be that way. 2  When someone acts a fool. ( 3 They are trippin'). 4  That girl is trippin' hard. 5  See more words with the same meaning: to do hallucinogens (e.g. LSD) .