/meem/ n. [coined by analogy with 'gene', by Richard Dawkins] An idea considered as a replicator, esp. with the connotation that memes parasitize people into propagating them much as viruses do. Used esp. in the phrase 'meme complex' denoting a group of mutually supporting memes that form an organized belief system, such as a religion. This lexicon is an (epidemiological) vector of the 'hacker subculture' meme complex; each entry might be considered a meme. However, 'meme' is often misused to mean 'meme complex'. Use of the term connotes acceptance of the idea that in humans (and presumably other tool- and language-using sophonts) cultural evolution by selection of adaptive ideas has superseded biological evolution by selection of hereditary traits. Hackers find this idea congenial for tolerably obvious reasons.
One big difference between memes and genes is that memes are processed and possibly improved by the people that hold them - something that cannot happen to genes. It is this advantage that the memetic algorithm has over simple genetic or evolutionary algorithms.
These algorithms are useful in solving complex problems, such as the "Travelling Salesman Problem," which involves finding the shortest path through a large number of nodes, or in creating artificial life to test evolutionary theories. Memetic algorithms are one kind of metaheuristic.