Intense sexual activity without penetration - cf intercourse. Can include mutual masturbation, oral sex, and so on. While one still has to be cautious with regard to disease and pregnancy, outercourse, in its many many flavors, is a fun alternative to vanilla sex. Definitely teaches the enjoyability of foreplay, and rather reduces the overwhelming emphasis our culture places on the crude mechanics of sex. Plus, useful for avowed virgins-til-marriage (especially if there's a long engagement . . . or just a lot of chemistry).