1. The coming or arrival, especially of something extremely important: the advent of the computer.
2.1. The liturgical period preceding Christmas, beginning in Western churches on the fourth Sunday before Christmas and in Eastern churches in mid-November, and observed by many Christians as a season of prayer, fasting, and penitence.
2.2. Christianity. The coming of Jesus at the Incarnation.
2.3. Christianity. See Second Coming.
Etymology: [Middle English, the Advent season, from Old French, from Latin adventus, arrival, from past participle of advenīre, to come to : ad-, ad- + venīre, to come.]
Now that we are almost at the middle of advent, the word reminded me of adventitious roots and yes, they are somewhat related:
1. Not inherent but added extrinsically. See synonyms at accidental.
2. Biology. Of or belonging to a structure that develops in an unusual place: adventitious roots.
Etymology [From Latin adventīcius, foreign, from adventus, arrival. See advent.]