GMO stands for genetically modified organism. This term refers to organisms which have been genetically manipulated by modern molecular genetics techniques. Typically, the manipulation involves the incorporation of a foreign gene into the genome of the target organism.
This wiki focuses primarily on genetically modified plants used in agricultural, but GMO animals and microbes exist as well.
As discussed in the article about precise genome modification, it is now possible to engineer a plant to have DNA sequence matching what one could obtain through traditional breeding or natural mutation. Advances like this are making it less clear what qualifies as genetically modified organism as legal, scientific and conventional definitions diverge.