"Beef" is used as an adjective, when the right word is "Beefy".
It's not really a gate but random encounters or high level patrolling monsters to keep a player from going some place until later.
Has been misunderstood to be a gate made of beef.
The nature of the trope makes a truly exact name hard to pull off.
It generally carries across the idea of the trope, that of a barrier (Gate) based on strength, (Beef) both yours (You have to be this strong to pass) and your opponents. (They are strong to keep you from going where you shouldn't.)