What does suile mean in Gaelic?

"Suile" is not a Gaelic word. It is likely a misspelling of "sùilean" which means "eyes" in Scottish Gaelic.

The word for "eye" in singular form is "sùil".

It's important to note that there are variations in spelling and pronunciation between Scottish Gaelic and Irish Gaelic, so the word for "eye" might be slightly different in Irish Gaelic.