a lilly is a wonderful person and a dear friend. it comes from the flower lily because the friendship she holds is just as pure as these beautifulflowers.
A girl that only has had sex with one person and does not want to partake in sex with anyone else much like Lilly in the popular Tv show how i met your mother.
The one friend in the group conversation in a public setting where when there is silence they continue to talk about something nobody cares about and is completely off topic.
While at the dinner party, Jake decided to make everythingawkward by pulling a Lilli right before we left.