The term "One Shot" has evolved to be all-encompassing for any sound format that plays a single time.
Commonly an "instrument one shot" is a .wav file of a sound recorded as a single note that can be loaded up into your DAW sampler and played (or clicked in) as an instrument.
"Accents" are often a multi-layered, melodic flourish that can add interest and can be chopped and flipped just as easily as a full melody sample.
Other terms you may see include "chord shot" (being a single chord rather than note) and "texture" (sometimes short, sometimes long piece of audio leaning towards a more tactile tone).