Any 8-cell polyomino. There are 369 such objects. The
word is particularly applied to the following octomino (or its
two-generation successor), which is fairly common but lacks a proper
name:
Game of Life Explanation
The Game of Life is not your typical computer game. It is a cellular
automaton, and was invented by Cambridge mathematician John Conway.
This game became widely known when it was mentioned in an article
published by Scientific American in 1970. It consists of a grid of
cells which, based on a few mathematical rules, can live, die or
multiply. Depending on the initial conditions, the cells form various
patterns throughout the course of the game.
Rules
For a space that is populated:
Examples
Each cell with one or no neighbors dies, as if by solitude.
Each cell with four or more neighbors dies, as if by
overpopulation.