Pushdown

Since indexed grammars are context-free grammars with pushdowns, the generalization of Thatcher's result shows that they generate the yields of the tree languages recognized by deterministic pushdown tree automata.

Source: wiktionary

filter pushdown

Source: wiktionary

predicate pushdown

Source: wiktionary

Machine exercises with weight stacks, like pushdowns or pulldowns, are ideal for cranking out more than three drops because all you need to do is insert the pin in a higher (lighter) slot each time.

Source: wiktionary