Used to indicate that something happens or is done before another event. Often appears in the phrase ～に先立ち (prior to ~).
出発に先立ち、準備を整えた。
Prior to departure, we made preparations.
会議に先立ち、資料を配布します。
Before the meeting, we will distribute the materials.
standing on tiptoes; tiptoe stance
Derived from the verb 先立つ (さきだつ, 'to precede'), with the continuative form used as a noun/adverb.