"Supinated grip" refers to a way of holding something, like a bar or a dumbbell, where your palm is facing upward or facing towards you. Full definition
Supinated grip actually means that you grip the weight with your palms pointed upwards, probated means you grip the weight with your palms facing down and semi-supinated means that the palms are facing each other when performing the exercise. (fitnessandpower.com)
Comparing the effect of forearm orientation, Youdas et al. (2010) compared the pronated grip pull - up and supinated grip chin - up. (strengthandconditioningresearch.com)
The main two variations are the chin - up (supinated grip) and the neutral pull - up (palms facing each other). (fitnessandpower.com)