from The American Heritage® Dictionary of the English Language, 4th Edition
- adv. Side by side: ships docked two abreast.
- adv. Up to date: keeping abreast of the latest developments.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adv. : At the same time; simultaneously
from the GNU version of the Collaborative International Dictionary of English
- adv. Side by side, with breasts in a line.”
- adv. Side by side; also, opposite; over against; on a line with the vessel's beam; -- with of.
- adv. Up to a certain level or line; equally advanced.
- adv. At the same time; simultaneously.
from The Century Dictionary and Cyclopedia
- Side by side, with breasts in a line: as, “the riders rode abreast,” Dryden.
- Nautical: Lying or moving side by side, with stems equally advanced. When used to indicate the situation of a vessel in regard to another object, opposite; over against; lying so that the object is on a line with the beam: in this sense with of.
- Figuratively, up to the same pitch or level: used with of or with: as, to keep abreast of the times in science, etc. At the same time; simultaneously.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. being up to particular standard or level especially in being up to date in knowledge
- adv. alongside each other, facing in the same direction
From Middle English a ("on") + brest ("breast"), in sense “breasts (chests) in line, side-by-side and exactly equally advanced”; roughly “breast-by-breast”. (Wiktionary)