For those of us who are language-challenged, international road signs are a very good thing. If I'd seen these words without a picture, I wouldn't have known what they were telling me. It would have been a "fingers crossed" moment.
Sometimes pictures are better than words.
The symbol looks to me like it is warning of slippery conditions. Google Translate told me the words "halt i bleytu" (in Icelandic) translates to "halt in wet conditions".
If you'd like to hear the translation, click here, then click on listen under the words.