Stack allocation means run-time allocation and deallocation of memory(1) in last-in/first-out order.
Typically, stack allocation is performed on top of the main stack, but one can have a separate data stack for this purpose as well, as in Forth, or even multiple ones, as in the PostScript language.
Allocation and deallocation are typically fast, since they can be done simply by adding or subtracting the size of the block from the stack pointer.
Using only stack allocation, without heap allocation, is somewhat restrictive, as only objects whose size is known at compile-time can be returned from a procedure.
Some programming languages (such as some versions of Lisp and C) provide program-controlled stack allocation and deallocation of dynamic extent objects for efficiency, despite its being unsafe.