1 extreme, excessive, severe, strong, great, fierce, harsh, acute, powerful, profound, deep:
The intense heat kept the firemen at bay.
2 eager, enthusiastic, keen, earnest, sincere, heartfelt, deep, passionate, impassioned, ardent, zealous, animated, burning, consuming, fervent, fervid, perfervid, vehement, frantic, fanatical, frenzied:
I had an intense desire to see the culprit brought to justice.
3 highly-strung or Chiefly US high-strung, emotional, temperamental, tense, touchy, testy, volatile, hysterical, hotheaded, feverish, nervous, (high-)spirited, impetuous, impulsive, Colloq uptight:
I appreciate his enthusiasm, but I wish Henshawe were a bit less intense about his politics.