A person who goes somewhere for a short visit and comes back the same day — usually for fun. It is British English, and it almost always comes as "day tripper": someone who takes a bus or train to the beach or a famous town in the morning and is home by night. Notice the small feeling in it: local people often say it with a light complaint. Trippers fill the streets, buy an ice cream, take photos, and leave no money in the hotels — so "the town is full of trippers" can sound a little tired or annoyed. It is not a rude word, but it is not a compliment either. Americans mostly do not use it this way; they would say "day-trippers" or just "visitors". There is a second, much more slangy use, from the drug meaning of "trip": a tripper is someone taking LSD. That use is old-fashioned now, mostly 1960s-70s, but you may meet it in songs and books.

一日遊的遊客、當天來回的旅客（英式用法，語氣常帶點嫌吵嫌擠的意味）