Definitions of throb:

• noun:   an instance of rapid strong pulsation (of the heart)

  Example: "He felt a throbbing in his head"

• noun:   a deep pulsating type of pain
• verb:   pulsate or pound with abnormal force

  Example: "My head is throbbing"

• verb:   expand and contract rhythmically; beat rhythmically
• verb:   tremble convulsively, as from fear or excitement