You can look up the meanings of peidio in any Welsh dictionary. A common meaning is 'to refrain from'.
neu (or) causes a soft mutation, which is why the p- has mutated to b- in the sentence.
I'm sorry; I was assuming that neu did not cause mutation, so I did not find it. Thank you.
Dim problem! The Ap Geiriaduron smart-phone dictionary app, the on-line Gweiadur and the on-line Geiriadur Prifysgol Cymru (and its GPC app) will all let you look up a mutated word and show the unmutated word and its meanings.