directly vs head-on

directly

adv
  • In a direct manner; in a straight line or course. 

  • Soon; next; in due time; as soon as it becomes convenient. 

  • Plainly, without circumlocution or ambiguity; absolutely; in express terms. 

  • Straightforwardly; honestly. 

  • In a straightforward way; without anything intervening; not by secondary but by direct means. 

  • Exactly; just; at the shortest possible distance. 

conj
  • As soon as; immediately (elliptical for directly that/as/when) 

head-on

adv
  • With direct confrontation. 

  • With the front of a vehicle. 

adj
  • Of a collision, from the front or in the direction of motion. 

  • Direct, abrupt, blunt or unequivocal; not prevaricating. 

noun
  • A collision from the front. 

How often have the words directly and head-on occurred in a corpus of books? (source: Google Ngram Viewer )