Lewis & Short

aestīvus, a, um, adj. [aestas],

  1. I. of or pertaining to summer, summer-like, summer (freq. and class.): Quo pacto aestivis e partibus Aegocerotis Brumalīs adeat flexus, turns from the hot region of heaven to the wintry sign of Capricorn, Lucr. 5, 615; so id. 5, 639: aestivos menses rei militari dare, hibernos juris dictioni, Cic. Att. 5, 14: tempora, dies, summer time, summer days, id. Verr. 2, 5, 31: sol, Verg. G. 4, 28: aura, Hor. C. 1, 22, 18: umbra, Ov. M. 13, 793: rus, Mart. 8, 61: per aestivos saltus deviasque calles exercitum ducimus, through woods, where flocks were driven for summer pasture, Liv. 22, 14: aves, summer birds, id. 5, 6: animalia, the insects of summer, Plin. 9, 47, 71, § 154: expeditiones, which were undertaken in summer, Vell. 2, 114: castra, a summer camp (constructed differently from a winter camp), Suet. Claud. 1.
    Hence,
  2. II. Subst.: aestīva, ōrum, n.
    1. A. For a summer camp, τὰ θερινά: dum in aestivis essemus, Cic. Att. 5, 17; id. Fam. 2, 13: aestiva praetoris, of a pleasure-camp, pleasurehouse, Cic. Verr. 2, 5, 37.
    2. B. The time appropriate for a campaign (cf. aestas; often continuing until December; v. Manut. ad Cic. Fam. 2, 7); hence, a campaign, Cic. Pis. 40: aestivis confectis, after the campaign was ended (which did not take place until the Saturnalia, XIV. Kal. Januar.), id. Fam. 3, 9 fin.: perducere aestiva in mensem Decembrem, Vell. 2, 105.
    3. C. Summer pastures for cattle: per montium aestiva, Plin. 24, 6, 19, § 28.
      Meton. for the cattle themselves: Nec singula morbi Corpora corripiunt, sed tota aestiva, Verg. G. 3, 472.
      Hence, * adv.: aestīvē, in a summer-like manner, as in summer: admodum aestive viaticati sumus, we are furnished in a very summer-like manner with money for our journey, i. e. we have but little (the figure taken from the light dress of summer; or, acc. to others, from the scanty provisions which soldiers took with them in summer), Plaut. Men. 2, 1, 30.