eyot or ait (AYT, AHY-uht) - n., a small island, especially in a river or lake.
Alternate spellings of the same word, which in Middle English was most often spelled eyt or eit, and in Old English, ȳgett or iggath or igeth, all of which are alternate spellings of the diminutive of īg, ēg, or ieg, meaning island -- and which in fact forms the is- of Modern island. Eyot is the more common form today, except when referring to certain islands in the Thames, which are aits. Can also be called an islet or holm.
Appletree Eyot, in the River Thames at Reading, Berkshire:
And for a usage example, let's go with Tolkien: “That night they camped on a small eyot close to the western bank”