Buffer overflow is a term used to describe when data is put in storage but the size of the data is excessively large (for example: a text string over the maximum number of characters supported by the game).
The term could for example describe a glitch where data has an excessively long name and the name overflows to corrupt unrelated memory addresses, or the game copying more data than it is supposed to.
In the Pokémon games
The latter example of the game copying more data than it is supposed to occurs with many buffer overflow glitches in Pokémon Red, Blue, and Yellow.
These are listed below, as such:
In addition, Super Glitch from moves in Generation III may be caused by a buffer overflow from the move's excessively long name and Pokémon News Reporter corruption is a corruption technique caused by a glitch Pokémon's excessively long name.
ZZAZZ glitch is also caused by the game writing beyond the payout money pointer at D079 (D078 in Yellow).
Another glitch which exploits the expanded party, known as "wild appeared!" occurs when the game attempts to set values relating to the Poké Ball graphics representing the state of the player's Pokémon beyond the normal buffer of six Pokémon.