From AMS Glossary
Any strengthening or development of anticyclonic circulation in the atmosphere; the opposite of anticyclolysis.
This applies to the development of anticyclonic circulation (or the initial appearance of a high) where previously it was nonexistent, as well as to intensification of existing anticyclonic flow. The most common application of this term is to the formation of a new anticyclone. Care should be taken, however, to distinguish the increase in anticyclonic circulation from the increase in atmospheric pressure (filling), although they usually occur simultaneously.