Byrstr

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

byrstr

pp. set with bristles; fig. exasperated.

Possible runic inscription in Younger Futhark:ᛒᚢᚱᛋᛏᚱ

Also available in related dictionaries:

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

• Old Norwegian - Johan Fritzner's Dictionary