lit. to sing “The Empty City Stratagem” (idiom) / fig. to put up a bluff to conceal one's weakness / (jocular) (of a place etc) to be empty / (of one's stomach) to be rumbling
the empty city stratagem (in which Zhuge Liang presents himself as unperturbed while making it evident that his city is undefended, hoping his adversary will suspect an ambush) / double bluff