The welsh crumble symbolises the proverbial spineless welsh man combining the words "crumble" and the dirty term "welsh".
Used in context -
"That Jonathan Russell, he's a welsh crumble" - meaning he is spineless or weak; or
"crouch, set, bind, engage, welsh crumble" - referring to the welsh scrum; or
"i'm going to turn her vagina into a welsh crumble" - referring to a dirty welsh pudding.
Notably, very similar to the term "wetty", "wet lettuce" or "pussyhole" alike, and can be used in similar ways.
"That Jonathan Russell, he's a welsh crumble" - meaning he is spineless or weak; or
"crouch, set, bind, engage, welsh crumble" - referring to the welsh scrum; or
"i'm going to turn her vagina into a welsh crumble" - referring to a dirty welsh pudding.