Grimmast

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

grimmast

(d and að), v. refl. to chafe, be furious (g. móti guði).

Possible runic inscription in Younger Futhark:ᚴᚱᛁᛘᛘᛅᛋᛏ

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