noun, noun or participle which takes 'suru', intransitive verb
being busy with; being occupied with
Literary and rare; used for being deeply engaged or absorbed in work or duties. Often appears in formal or classical contexts.
彼は公務に鞅掌している。
He is busy with public duties.
忙しい is the common everyday word for 'busy'. 鞅掌 is a rare, literary term for being absorbed in work.
The exact derivation is uncertain; the kanji 鞅 (horse's bellyband) and 掌 (palm) are used in this compound with a meaning that is not directly related to their individual senses.