Synonyms for Think hard:

• v.

  •concentrate (verb)
  • settle,
  • apply,
  • intensify,
  • center,
  • meditate,
  • muse,
  • head trip,
  • attend,
  • examine,
  • contemplate,
  • peruse,
  • focus,
  • ponder,
  • weigh,
  • study,
  • scrutinize,
  • establish,
  • put,
  • knuckle down,
  • bring to bear,
  • set,
  • need,
  • ruminate,
  • sweat.
  •puzzle (verb)
  • cudgel,
  • marvel,
  • brood.

• Other synonyms:

  •Other relevant words:
  • puzzle over,
  • stew,
  • hammer out.