Fussy definition is rather hard to grasp. It refers to someone who is immensely meticulous and fault-finding. A persnickety individual often nitpick and has high standards when it comes to standards and flawlessness. Their fastidious nature can be regarded as praiseworthy, but it can also intensify extreme criticism and unnecessary dissatisfaction. Being persnickety is typically associated with detailed attention to detail but can also be seen as a manifestation of pedantry.
