What is meant by sam spade and define it?

Sam Spade is a fictional character who is the protagonist of Dashiell Hammett's novel The Maltese Falcon (1930) and the various films and adaptations based on it, as well as in three lesser known short stories written by Hammett. The novel, first published as a serial in the pulp magazine Black Mask, is the only one that Spade appears in, yet the character is widely cited as the crystallizing figure in the development of the hard-boiled private detective genre – Raymond Chandler's character Philip Marlowe, for instance, was strongly influenced by Hammett's Spade. Spade was a departure from Hammett's nameless and less than glamorous detective, The Continental Op.

Sam Spade combined several features of previous detectives, most notably his cold detachment, keen eye for detail, and unflinching determination to achieve his own justice. He is the man who has seen the wretched, the corrupt, the tawdry side of life but still retains his "tarnished idealism". Sources: