It refers to first cousins. Second cousin marriage was so common, especially in the Fife fishing communities, that it wasn't commented on. I believe the older generation used to refer to second cousins as "cousins' bairns".
It's often useful to the genealogist to be told that a married couple were cousins, especially in a small community with only a few surnames.
Where I come from, a lot of people have detailed family trees and will tell you gleefully that they are descended twice or three times from the same individual, such was the prevalence of cousin marriages. I'm descended twice from a couple called Thomas Watson and Ann Craigie who were married in 1715, through their sons David and William. Moreover, I know where Thomas and Ann lived and it was only a few minutes' walk from the house I was brought up in.
My avatars are my great-grandparents James Murray Watson and Margaret Watson, distant cousins who were descended respectively from David Watson and William Watson.
Harry