CAMPAIN, noun 1. An open field; a large open plain; an extensive tract of ground without considerable hills. [See Champaign.] 2. The time that an army keeps the filed, either in action, marches, or in camp, without entering into winter quarters. A campaign is usually from spring to autumn or winter; but in some instances, armies make a winter campaign. CAMPAIGN, verb intransitive To serve in a campaign.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI