This is the final part of a three-part essay on fuzziness in medieval literary language. Each part corresponds broadly to Clifford Geertz's trifold instances of blur as involving “face-to-face interaction” (“life as game”), “collective intensities” (“life as stage”), and “imaginative forms” (“life as text”). Part 3 considers what Geertz might mean by describing text as a “dangerously unfocused term,” through discussing how bilingualism is negotiated in poetry. Three areas of vagueness are explored: the linguistic boundaries in a bilingual poem, the definition of a poem in the trilingual culture of insular medieval writing, and the relationship between literary and ordinary language. Examples are taken from a fifteenth-century bilingual carol, an early fourteenth-century trilingual poem, a bilingual sermon, a passage of love-writing discovered in the midst of a fifteenth-century legal roll, and finally a pair of French poems about the death of the English commander, Thomas Montagu, fourth earl of Salisbury, at the English siege of Orléans in 1428, contrasted with some English translations of poems by Charles d'Orléans. The essay argues that blurriness in medieval bilingualism gives us a fresh way of approaching primary questions about poetry and the literary.