/ əˈvɜː(r); NAmE / verb
( -rr- ) ( formal ) to state firmly and strongly that sth is true
SYN assert , declare :
[ v that ]
She averred that she had never seen the man before.
[also vn , v speech ]
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WORD ORIGIN
late Middle English (in the sense declare or confirm to be true ): from Old French averer , based on Latin ad to (implying cause to be ) + verus true.