tertial

American Heritage® Dictionary of the English Language, Fourth Edition

1. adj. Of, relating to, or designating the third row of flight feathers on the basal section of a bird's wing.
2. n. A tertial feather.

Century Dictionary and Cyclopedia

1. Of the third rank or row among the flight-feathers of a bird's wing; tertiary, as a quill-feather.
2. n. A tertiary flight-feather; one of the pennæ, or large feathers, of a bird's wing of the third set, which grow on the elbow or upper arm; one of the tertiaries. The word was intended to signify only the third set of flight-feathers, in the same relation to the humerus that the secondaries bear to the ulna, and the primaries to the manus; but in practice two or three of the innermost secondaries are called tertials when in any way distinguished from the rest. Also tertiary, tertiary feather. See cuts under bird and covert, n., 6.

Wiktionary

1. n. ornithology Any flight feather attached to the humerus (upper arm) of a bird.

GNU Webster's 1913

1. (Zoöl.) Same as tertiary.