Fig. a long and detailed period of questioning. (*Typically: get ~; give someone ~.) Why is it I get the third degree from you every time I come home late? Poor Sally spent all night at the police station getting the third degree.
Intensive questioning or rough treatment used to obtain information or a confession, as in The detectives gave her the third degree, or Jim gave her the third degree when she came home so late. This term comes from freemasonry, where a candidate receives the third or highest degree, that of master mason, upon passing an intensive test. Dating from the 1770s, the phrase was transferred to other kinds of interrogation in the late 1800s.
n. a session of questioning, usually by the police. Bart got the third degree, but—being the thoroughbred he is—he was a clam. They gave Spike the third degree, but he refused to say anything.