also: ぎっちり
adverb, adverb taking the 'to' particle
tightly packed; densely; crammed
Describes a space filled to capacity with little or no room to spare; often used for schedules, containers, or crowds.
箱の中に本がぎっしり詰まっている。
The box is tightly packed with books.
今日の予定はぎっしりだ。
Today's schedule is jam-packed.