| 1. | a large gland in most cephalopods, as the cuttlefish, octopus, and squid, that is near the rectum and ejects ink at predators. |
| 2. | a flexible structure containing ink. |
| ink sac n. An ink-containing organ located near the rectum in most cephalopods, including the octopus, squid, and cuttlefish. |