Definition of "unimpassive"

Jack was called plucky, and he was, but it took all the strength of will that the slim, resolute engineer possessed, to hold him to his purpose, when he faced about and surveyed the unimpassive faces which compassed him.

1899, Martha Frye Boggs, Jack Crews, page 237

Yet the lecturer exhibited no sign of physical emotion, used no gesture, and the unimpassive face with the veiled eye added infinitely to the solemnity of the discourse, which seemed hieratic and liturgical rather than oratorical.

1911, The Cornhill Magazine, page 534