Rush is an old term for the period of a semester in which non-greek students can observe organized events sponsored by the different chapters on campus.  This is the traditional period in which a person can pick a chapter would like to join.  However, the name is misleading, Don't rush into any decision.. 

You can decide to join any chapter at any time.

Lycoming College has "Open Bid".  This simply means that you can take as long as you wish to get to know a chapter at your own pace.  Make friends and eventually if you decide that "going Greek" is for you, you can join. 

In either process you have to be asked to join through the "Bidding" process.  If you are given a bid from a chapter you have the option of accepting or declining.