If you say that someone is fastidious, you mean that they are concerned about keeping clean to an extent that many people consider to be excessive. Be particularly fastidious about washing your hands before touching food. + fastidiously fas·tidi·ous·ly Ernestine kept her daughters fastidiously clean. very careful about small details in your appearance, work etc = meticulous (fastidiosus, from fastidium )
giving and careful attention to detail; hard to please; excessively concerned with cleanliness; "a fastidious and incisive intellect"; "fastidious about personal cleanliness"
having complicated nutritional requirements; especially growing only in special artificial cultures; "fastidious microorganisms"; "certain highly specialized xerophytes are extremely exacting in their requirements
If you say that someone is fastidious, you mean that they pay great attention to detail because they like everything to be very neat, accurate, and in good order. her fastidious attention to historical detail He was fastidious about his appearance. = meticulous