ac·i·nus / ˈasənəs/ • n. (pl. -ni / -ˌnī/ ) Anat. 1. a small saclike cavity in a gland, surrounded by secretory cells.2. a region of the lung supplied with air from one of the terminal bronchioles.

acinus (pl. acini) The smallest unit of a multilobular gland, such as the pancreas. Each acinus in the pancreas is made up of a hollow cluster of acinar cells, which produce the digestive enzymes secreted in pancreatic juice. Minute ducts from the pancreatic acini eventually drain into the pancreatic duct.

acinus (ass-in-ŭs) n. (pl. acini)
1. a small sac or cavity surrounded by the secretory cells of a gland.

2. (in the lung) the tissue supplied with air by one terminal bronchiole.
—acinous adj.