Wiktionary
tamasic
a. Relating or conforming to tamas (one of the gunas in Hindu philosophy).
Usage examples of "tamasic".
But when the physical brain flags and refuses to support the effort of the will and mind, then you find a dull and Tamasic condition in Sadhana intervenes.
I do not know what it is physiologically, but it is a condition of Tamasic withdrawal into the inner consciousness.