NTC full form stands for Negative Temperature Coefficient that is a characteristic of a material for which resistance, length, some other characteristic of a material decreases with the increasing of temperature.
As the conductive material has a positive temperature coefficient and the resistance increase with the increase of temperature. But when we talk about semiconductor material resistance decrease with the increases of temperature due to negative temperature coefficient characteristic.
When the temperature of semiconducting material is increased then the charge-carrier of the semiconductor increases. When the increasing conductivity causes the decreasing of resistance and this phenomenon of semiconductor is known as the negative temperature coefficient of resistance for semiconductor.
Another NCT full form in academic is New Theological College.