1. in a way that shows great attention to detail and accuracy; very carefully and precisely
2. in a way that shows concern about cleanliness, neatness, or propriety; fussily

Examples

• She fastidiously organized her desk before starting work.
• The chef fastidiously arranged each ingredient on the plate.
• He fastidiously cleaned his glasses every few minutes.
• The accountant fastidiously checked every calculation twice.
• She fastidiously avoided stepping on the cracks in the sidewalk.
• The librarian fastidiously maintained the card catalog system.
• He fastidiously folded his clothes and placed them in neat piles.