The act of pleasuring oneself with Nickelodeon's trademarked Gak product; preferably while watching any Nickelodeon, Snick, Nick at Night, Nicktoons, TeenNick or Nick Jr. program (Double-Dare, All That, Power Rangers, etc.)
I won't be able to make it to the party this evening. There is a Are You Afraid of the Dark marathon on Nickelodeon that I will be Gaking-off to all night.
To stimulate ones tits or ass while pleasuring their self. Alternatively "gaking-off" can be used for a direct substitution of "fucking about", "dicking around", "wasting time", making one's own potions by hand instead of efficiently or effectively.
"I thought we were going out last night but i walked into his room while he was gaking-off covered tits to ass with cocoanut oil and peanut butter. Poor Holly".
"The rest of the team is all geared up waiting to start the raid, but he's gaking-off mixing clean rannar weeds with vials of water".