HOW I MET YOUR MOTHER “Definitions” Season 5 Premiere September 20, 2009 How I Met Your Mother Watch a sneak peek of HOW I MET YOUR MOTHER “Definitions” season 5 premiere airing Monday, Sept. 21 10:00pm ET/PT. Episode Synopsis: HOW I MET YOUR MOTHER “Definitions” Season 5 premiere – When Marshall (Jason Segel) and the gang finds out that Barney (Neil Patrick Harris) and Robin (Cobie Smulders) are hesitant to define their relationship, Lily (Alyson Hannigan) forces them to confront their biggest fear. Meanwhile, Ted (Josh Radnor) is anxious about teaching his first lecture at Columbia, on the fifth season premiere of HOW I MET YOUR MOTHER, Monday, Sept. 21 (8:00-8:30 PM, ET/PT) on the CBS Television Network. Online Episodes: catch up on any How I Met Your Mother episodes that you may have missed by clicking here. Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on Reddit (Opens in new window)Click to share on Google+ (Opens in new window)Click to share on Tumblr (Opens in new window)Click to share on Pocket (Opens in new window)