ACK TCP acknowledgment.
address A memory location.
aggregation A grouping of data. The term is usually used in the DTrace/SystemTap context, referring to a grouping of data into buckets.
API Application programming interface.
application A program, typically user-level.
array A set of values. This is a data type for programming languages.
associative array A data type for programming languages where values are referenced by an arbitrary key, which may be a text string.
AT&T The American Telephone and Telegraph Company, which included Bell Laboratories, where ...