Completely neat and clean "the apartment was immaculate"; "in her immaculate white uniform" - speckless, spick-and-span, spic-and-span, spic, spick, spotless
Free from stain or blemish - undefiled
Without fault or error "timing and technique were immaculate"; "an immaculate record" - faultless, impeccable
See also: clean, immaculately, immaculateness, perfect, pure