acephalia
acephalism
acephaly

Following Frondizi's overthrow in 1962, he lad diplomatic efforts to have other members of the Organization of American States recognize the government of President José María Guido, who had been appointed in Frondizi's stead via the acephaly clause.

The calculating López Rega seized on this to prevail on Vice President Vicente Solano Lima and Senate President Alejandro Díaz Bialet to resign, as well, leaving a constitutional vacuum referred to as an "acephaly" - the absence of a head of state.