headlong vs smack dab

headlong

verb
  • To precipitate. 

adj
  • Rushing forward without restraint. 

  • Precipitous. 

  • Reckless, impetuous. 

  • Plunging downwards head foremost. 

adv
  • With an unrestrained forward motion. 

  • Rashly; precipitately; without deliberation; in haste, hastily. 

  • With the head first or down. 

smack dab

How often have the words headlong and smack dab occurred in a corpus of books? (source: Google Ngram Viewer )