a short trip or outing to some place, usually for a special purpose and with the intention of a prompt return: a pleasure excursion; a scientific excursion.
2.
a trip on a train, ship, etc., at a reduced rate: weekend excursions to mountain resorts.
3.
the group of persons making such a journey: an excursion of tourists.
4.
a deviation or digression: excursions into futile philosophizing.
5.
Physics.the displacement of a body or a point from a mean position or neutral value, as in an oscillation.
6.
an accidental increase in the power level of a reactor, usually forcing its emergency shutdown.
1570s, "a deviation in argument," from L. excursionem (nom. excursio) "a running forth, excursion," from excursum, pp. of excurrere "run out," from ex- "out" + currere "to run" (see current). Sense of "journey" recorded in English by 1660s.