verb

• (ambitransitive) To assert the truth of (something); to affirm (something) with confidence; to declare (something) in a positive manner.
  "A rare thing to ſee a yong man or woman, that liues idlely, and fares well, of what condition ſoeuer, not to bee in loue. Vbicumqꝫ ſecuritas, ibi libido dominatur, luſt & ſecurity domineere together, as Sᵗ Hierome auerreth."
• (ambitransitive, law) To justify or prove (an allegation or plea that one has made).
• (transitive, obsolete) To avouch, prove, or verify the existence or happening of (something), or to offer to do so.
  "[…] I return'd with ſimular proofe enough, / To make the Noble Leonatus mad, / By wounding his beleefe in her Renowne, / With tokens thus, and thus: auerring notes / Of Chamber-hanging, Pictures, this her Bracelet / (Oh cunning how I got) nay ſome markes / Of ſecret on her perſon, that he could not / But thinke her bond of Chaſtity quite crack'd, / I hauing tane the forfeyt."

noun

• (British, dialectal, archaic) A beast of burden; chiefly a workhorse, but also a working ox or other animal.
• (Northern England, Scotland, dialectal, archaic) An old, useless horse; a nag.
  "[…] Gilbert has but two half-starved cowardly peasants to follow him, and but an auld jaded aver to ride upon, fitter for the plough than for manly service; […]"