n.1 a ball of mixed aromatic substances placed in a cupboard etc. or hist. carried in a box, bag, etc. as a protection against infection.
2 a (usu. spherical) container for this.
3 a spiced orange etc. similarly used.
Etymology: earlier pom(e)amber f. AF f. OF pome d'embre f. med.L pomum de ambra apple of ambergris