The practice of two people riding a single surfboard at the same time; specifically a type of surfing in which two people riding on the same surfboard perform a series of acrobatic feats (often as a competitive sport).
Origin
1930s.
Definition of tandem surfing in US English:
tandem surfing
noun
The practice of two people riding a single surfboard at the same time; specifically a type of surfing in which two people riding on the same surfboard perform a series of acrobatic feats (often as a competitive sport).