Definition of pop-ups:
(adj) :
Operating or existing for a brief period only; temporary.
(n) :
(Internet) A pop-up advertisement; an advertisement that is triggered to appear on a computer screen when the user accesses a particular web page.
(n) :
A business that opens for a brief temporary period only, such as a temporary restaurant.
(adj) :
Coming into view suddenly from a concealed position.
(adj) :
Opening out to form a three-dimensional structure when the page of a book is opened.
(n) :
A folded paper element which pops up from a book, greeting card, etc.