| ACO | a poisonous herb native to northern Europe having hooded blue-purple flowers |
|---|---|
| ACO | used in some classifications for the genus Acorus which is usually assigned to Araceae |
| ACO | absence of the pupil in an eye |
| ACO | islands in the Atlantic Ocean belonging to Portugal |
| ACO | fruit of the oak tree: a smooth thin-walled nut in a woody cup-shaped base |
| ACO | barnacle that attaches to rocks especially in intertidal zones |
| ACO | cup-shaped structure of hardened bracts at the base of an acorn |
| ACO | small dark green or yellow ribbed squash with yellow to orange flesh |
| ACO | squash plant bearing small acorn-shaped fruits having yellow flesh and dark green or yellow rind with longitudinal ridges |
| ACO | a small vacuum tube |
| ACO | sweet flags |
| ACO | perennial marsh plant having swordlike leaves and aromatic roots |