noun A recipient of hospitality, especially someone staying by invitation at the house of another.
The guests were let in by the butler.
noun A patron or customer in a hotel etc.
Guests must vacate their rooms by 10 o'clock on their day of departure.
noun An invited visitor or performer to an institution or to a broadcast.
special guest
noun A user given temporary access to a system despite not having an account of their own.
noun Any insect that lives in the nest of another without compulsion and usually not as a parasite.
noun An inquiline.
verb To appear as a guest, especially on a broadcast.
verb As a musician: to play as a guest, providing an instrument that a band/orchestra does not normally have in its line up (for instance, percussion in a string band).