from The American Heritage® Dictionary of the English Language, 4th Edition
- n. An ancient unit of linear measure, originally equal to the length of the forearm from the tip of the middle finger to the elbow, or about 17 to 22 inches (43 to 56 centimeters).
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A unit of linear measure, no longer in use, originally equal to the length of the forearm.
from the GNU version of the Collaborative International Dictionary of English
- n. The forearm; the ulna, a bone of the arm extending from elbow to wrist.
- n. A measure of length, being the distance from the elbow to the extremity of the middle finger.
from The Century Dictionary and Cyclopedia
- n. In anatomy: The forearm or antebrachium; the arm from the elbow to the wrist.
- n. The inner bone of the forearm; the ulna.
- n. A linear unit derived from the length of the forearm.
- n. In entomology, one of the veins, nerves, or ribs of an insect's wing; a cubital rib, succeeding the radius or sector. See phrases under cubitus.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. an ancient unit of length based on the length of the forearm
Bottom line: A cubit is the distance between some two points, wherever they are in what ever country in whatever period of history -- maybe.
The word cubit means the length of the forearm from the elbow to the wrist, and in this statue of which we speak this part of the arm is made very prominent, and the measure itself is omitted.
The Egyptian cubit is about twenty — two inches of the English measure.
This ancient cubit is repeated 400 times in each basis of the great pyramid, and seems to indicate the primitive and universal measures of the East.
So even if the object had an exact circumference of 30 cubits (not a given since a cubit is a relative/approximate measurement depending on a person’s arm), we see that the diameter is indeed properly rounded up to 10 cubits, the asserted precision in Scripture.
¶ And these are the measures of the altar after the cubits: The cubit is a cubit and a handbreadth; even the bottom shall be a cubit, and the breadth a cubit, and the border thereof by the edge thereof round about shall be a span; and this shall be the higher place of the altar.
A cubit is the distance from elbow to fingertip; ordinary persons are usually four cubits tall.
And these are the measures of the altar by the truest cubit, which is a cubit and a handbreadth: the bottom thereof was a cubit, and the breadth a cubit: and the border thereof unto its edge, and round about, one handbreadth: and this was the trench of the altar.
 A cubit is the length from the elbow to the extremity of the middle finger, and therefore an indefinite measure, but modern usage takes it as representing a length of seventeen to eighteen inches.
The Egyptians did not use the sacred amma, or cubit, which is about twenty-five of our inches.