This is the 7966th most frequent Japanese word.
大儀
"大儀" means "ceremony" or "formality" and can also convey "great toil" or "effort" depending on context.
In this sentence, '大儀' is used to denote significant effort or diligence in accomplishing a task.
大儀をもって任務を遂行しました。
With great effort, the duty was accomplished.
Here, '大儀' is part of a proper noun, denoting an imperial title.
大儀天皇の御行幸を拝見しました。
I had the honor of witnessing Emperor Daigi's procession.
In this usage, '大儀' expresses a sense of tiredness or burden experienced physically or mentally.