She bought a white-ish dress that looks almost pure white in the sunlight.

white-ish 是由形容词 white（白色的）加上后缀 -ish 构成的。后缀 -ish 表示"略带...的""近似...的"，所以 white-ish 意思是"略带白色的"或"近似白色的"，可以翻译为"米白色的"。