Competitive means different things to different people.
But a generally accepted definition would be that a non-competitive program has a pattern of not filling its positions in the match.
Less competitive programs tend to be in less desirable geographic areas.
Some AMGs would say that less competitive programs have a high number of FMGs.
The problem with the above is that you don't know why these factors happen. Does a program have an open spot because they couldn't fill it or they preferred not to with the candidates available? If they couldn't fill it, why? Is the location undesirable, is it "malignant", is the education poor, the ancillary staff non-existent, etc.?
Word of mouth is usually helpful and your faculty and others before you can give you some inside tips/info on the above. But there is no centralized database of non-competitive programs or rankings of residencies.