noun, na-adjective, noun which may take the genitive case particle 'no'
perfunctory; going through the motions; done out of obligation
Describes an action, invitation, gift, or gesture done only because social obligation (義理) demands it, without real feeling or enthusiasm. Often used with の or な to modify nouns.
His perfunctory greeting lacked sincerity.
義理一遍な付き合いは疲れるだけだ。
A relationship that's just going through the motions is only tiring.
義理 is the general concept of social obligation or duty, while 義理一遍 specifically describes something done merely out of that obligation, without genuine feeling.
形式的 means 'formal' or 'ceremonial' and can overlap with 義理一遍, but 義理一遍 emphasizes the lack of sincerity due to social pressure, whereas 形式的 focuses on following a prescribed form.
A yojijukugo combining 義理 (social obligation) and 一遍 (once, one time, or merely). The phrase suggests doing something just once as a matter of duty, hence 'perfunctory'.