Looker was a term used to describe people believed to be good-looking.
James Skinsale opined that Leela was "not a bad looker". (TV: Horror of Fang Rock)
Rhys Williams acknowledged that his fiancée, Gwen Cooper, was a looker. (TV: Adam)
Jack Harkness recalled that Henry Parker used to be a looker. (TV: A Day in the Death)
At Gwen Cooper and Rhys Williams' wedding, Mervyn commented that "Carrie" was a looker, suggesting that she was on Gwen's side as he opined that Rhys' family did not have her "sort of style". Unbeknownst to him, "Carrie" was actually a Nostrovite in disguise. (TV: Something Borrowed)
Mona Lisa remarked that Giuseppe di Cattivo was "not much of a looker". (TV: Mona Lisa's Revenge)
Minnie Hooper commented that the Tenth Doctor was a looker. (TV: The End of Time)