tripper

(noun) (slang) someone who has taken a psychedelic drug and is undergoing hallucinations.

(noun) a walker or runner who trips and almost falls. Synonyms: stumbler.

(noun) a tourist who is visiting sights of interest. Synonyms: sightseer, excursionist, rubberneck.

(noun) a catch mechanism that acts as a switch. Synonyms: trip. Example: "The pressure activates the tripper and releases the water."