Spiritual energy.

("vitality"): the subtle energy produced through practice, especially the discipline of chastity (brahmacharya)

subtle vital force within the body which can lower immunity and vitality through forced orgasm, excessive and/or genitally focused ejaculation

Ojas is a Sanskrit word which literally means "vigor". It is the essential energy of the body which can be equated with the "fluid of life". According to Ayurveda, Ojas is the sap of our life energy which, when sufficient, is equated with immunity, and when deficient, results in weakness, fatigue and ultimately disease.