Ronald A. Mosocco, in his tome, "The Chronological Tracking of the American Civil War per the Official Records of the War of the Rebellion," in his preface, offers this:

"Commonly used terms in the Official Records - as you work your way through the pages, you will be aware of the frequent use of certain key words, the most frequent being the term 'skirmish.' Although the author has yet to find an exact definition, I believe it to mean all the encounters of hostile forces engaged in a fire fight on a small scale usually consisting of a thousand men or less.

"The reader will also note the repeated use of the following military terms: action, advance, affair, attack, battle, bombardment, campaign, capture, destruction, engagement, evacuation, expedition, occupation, operations, reconnaissance, retreat, scout, siege, surrender, withdraw, and so on."

George Martin