Definition of existimate in US English:

existimate

verb

rare, literary
  • with object To consider, think, regard; = "esteem".

Origin

Late Middle English; earliest use found in Treatise Arms. From classical Latin existimāt-, past participial stem of existimāre to value, esteem, to form or hold an opinion of, to judge, consider, to think, suppose from ex- + aestimāre.