| any projection that is thought to resemble a human arm | a measuring instrument for measuring angles to a celestial body; similar to a sextant but with 45 degree calibration |
| the graduated arc that is attached to an instrument for measuring angles | |
| either of the two halves of a bow from handle to tip | |
| one of the jointed appendages of an animal used for locomotion or grasping: arm, leg, wing, flipper | |
| (astronomy) the circumferential edge of the apparent disc of the sun or the moon or a planet | |
| any of the main branches arising from the trunk or a bough of a tree | |