to act or avail against with equal power, force, or effect; counteract.
2.
to furnish an equivalent of or a compensation for; offset.
3.
Archaic. to equal.
–verb (used without object)
4.
to be of equal force in opposition; avail.
Origin: 1350–1400; ME contrevailen < AF countrevail-, tonic s. (subj.) of countrevaloir to equal, be comparable to < L phrase contrā valēre to be of worth against (someone or something). See counter-, -valent
coun·ter·vail (koun'tər-vāl', koun'tər-vāl') v.
coun·ter·vailed, coun·ter·vail·ing, coun·ter·vails
v.
tr.
To act against with equal force; counteract.
To compensate for; offset.
v.
intr. To act against an often detrimental influence or power.
[Middle English countrevaillen, from Old French contrevaloir, contrevail- : contre-, counter- + valoir, to be worth (from Latin valēre, to be strong; see wal- in Indo-European roots).]