Provo is a slur used to describe Irish in a derogatory way. Shortened form of "Provisional Irish Republican Army (I.R.A.)" which is the most noted of the pro Northern Irish independence terrorist groups.
The word Provo is a racial slur that has been used historically to degrade and dehumanize irish. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to irish. If you are unsure about whether or not it is appropriate to use the word Provo, it is best to err on the side of caution and avoid using it in any situation.