Depends on context.
The conductor of a symphony orchestra, during rehearsal, would probably refer to that as unison doubled at the octave.
A music theory student would be chastised for calling it a chord. A chord must have three or more notes, by definition. However, it could be called an implied chord if the context justified it.
An atonal composer would refer to it as a simultaneity composed of a several pitches but only one pitch class.
A musician in a rock band trying to teach his group a song would probably not refer to it as a chord as that wouldn't really accurately tell them what to play. They would probably call it a note," e.g. a "C note."
A guitarist might call it a partial chord.
A computer programmer writing, say, an Ableton plugin, might call it a special case of a chord, and it would be reasonable for a chord generator to allow for chords composer only of a single note at various octaves.