flat character
a character, who can be summed up in a single sentence and acts as a function of only a few fixed character traits [and who is incapable of surprise, contradiction, and change through development]. A term coined by E. M. Forster in Aspects of the Novel (1927) in opposition to a round character. Forster’s aim is not to elevate the round at the expense of the flat, although he admits that the round is on the whole always a more interesting creation. Instead, he argues that there are compelling artistic reasons for a novelist to employ flat characters. And there are unquestionably great novelists, such as Dickens, who use only flat characters. (eForeword 2002) Also see round character