Sumarauki

As defined by A Concise Dictionary of Old Icelandic (Geir Zoëga):

sumarauki

m. ‘summer-eke’, an intercalary week, inserted every seventh year at the end of summer.

Possible runic inscription in Younger Futhark:ᛋᚢᛘᛅᚱᛅᚢᚴᛁ

Also available in related dictionaries:

This headword also appears in dictionaries of other languages closely related to Old Icelandic.

• Old Norse - Cleasby & Vigfusson Dictionary
• Old Norwegian - Johan Fritzner's Dictionary