Unbound

Unbound is an unloaded keyword. It's unusual because it isn't printed on any cards: instead, all companions that are not Ring-bound are unbound.

The Ring-bearer is always Ring-bound, even if it doesn't say so on their card. (This is only relevant with the alternate Ring-bearers, first introduced in Reflections.)

Only companions are unbound. Allies and minions can never be Ring-bound or unbound.

Cards that mention "unbound companions" are generally phrased that way to exclude the Ring-bearer from their effects. Cards that mention "unbound Hobbits" are generally meant to affect Merry and Pippin specifically. However, starting with the Shadows set, other unbound Hobbit companions are introduced, like Farmer Maggot, Hobbit of the Marish (11U163) and Fredegar Bolger, Fatty (18R107) .