偉効 is read as いこう (ikou) and means great effect.
いこう
ikou
ゆうこう
yuko (judo)
むこう
invalid
じこう
becoming invalid or void after a set time
じっこう
practical effect
はっこう
coming into effect
やっこう
medical efficacy
しっこう
lapse
こう
efficacy
じどうはっこう
self-executing (computer file)
しゅとくじこう
acquisitive prescription
たいせいこう
binding legal effectiveness as to third parties
とうせんむこう
invalidation of the election of a politician