extremely cowardly and mean; utterly unsportsmanlike
A strong yojijukugo condemnation of someone's character or behavior as both cowardly and underhanded. Often used in heated accusations.
That way of doing things is utterly cowardly and mean.
Everyone got angry at his extremely sneaky attitude.
Means 'cowardly' or 'unfair'; 卑怯千万 is a much stronger, emphatic version.
Means 'mean' or 'despicable'; 卑怯千万 adds the nuance of cowardice and is more dramatic.
A yojijukugo combining 卑怯 (cowardly, unfair) with the emphatic suffix 千万 (extremely). The exact origin is uncertain, but it follows a common pattern of intensifying a two-character word with 千万.