A recipient of hospitality, specifically someone staying by invitation at the house of another.
A patron or customer in a hotel etc.
An invited visitor or performer to an institution or to a broadcast.
A user given temporary access to a system despite not having an account of their own.
Any insect that lives in the nest of another without compulsion and usually not as a parasite.
An inquiline.
To appear as a guest, especially on a broadcast
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)
To receive or entertain hospitably.