It means to get married or commit to a monogamous relationship; probably the two most indicative words for the situation itself, born of a word that can mean "to move downward; sink, or descend," "to subdue," and "to conclude," and a word that means the "opposite of up."
"Man looks like Lester finally had to settle down and give up the player lifestyle...man, and settle isn't wrong!"
by Clint October 09, 2005
by catzo lungo May 26, 2003
verb. seh-tul down - 1) to stop knocking some one's fork on the floor especially at a cracker barrel. 2) to stop laughing uncontrollably to the point of endangering people within the area.
by Xwhite chocolateX January 09, 2010