What is the meaning of headlong?

adjective

• Excessively quick.
  • usage: "made a hasty exit"; "a headlong rush to sell"
  • synonyms: hasty
• With the head foremost.
  • usage: "a headfirst plunge down the stairs"; "a headlong dive into the pool"
  • synonyms: headfirst

adverb

• With the head foremost.
  • usage: "the runner slid headlong into third base"
  • synonyms: headfirst
• At breakneck speed.
  • usage: "burst headlong through the gate"
  • synonyms: precipitately
• In a hasty and foolhardy manner.
  • usage: "he fell headlong in love with his cousin"
  • synonyms: rashly