Sundrþykkjast

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

sundrþykkjast

v. refl. to fall out, quarrel.

Possible runic inscription in Younger Futhark:ᛋᚢᚾᛏᚱᚦᚢᚴᚴᛁᛅᛋᛏ