Meaning of the Sanskrit Word: tapasi

  tapasi—in penance    Bg 17.26, Bg 17.27, Bg 17.26-27, SB 2.9.7, SB 3.9.38, SB 3.21.45, SB 3.21.46, SB 3.21.47, SB 3.21.45-47
  tapasi—in severe austerities and penances    Madhya 22.42, Madhya 24.219
  tapasi—austerity    SB 4.23.4
  tapasi—in the austerity    SB 8.17.18
  tapasi—in austerities    SB 4.24.19
  tapasi—for austerities    SB 4.1.17

Can't find any compound Sanskrit words containing tapasi.