Academic Press

Academic Press (AP) is an academic book publisher of Elsevier specializing in scientific, technical, and medical literature. Founded in 1941 in New York City, it was acquired by Harcourt, Brace & World in 1969. Following Reed Elsevier's acquisition of Harcourt in 2001, Academic Press became part of Elsevier. Thus, Academic Press became an imprint of Elsevier.

From the Wikipedia article “Academic Press”, licensed under CC BY-SA 4.0.

An imprint is a brand inside a larger publishing house, often with its own editors and list. Imprints of large groups usually acquire through literary agents; read recent titles to see whether your book fits the list, then target agents who sell to it.