Compounds of 固い

• 固い
  (adj-i) (1) hard
  solid
  tough
  (2) stiff
  tight
  wooden
  unpolished (e.g. writing)
  (3) strong
  firm (not viscous or easily moved)
  (4) safe
  steady
  honest
  steadfast
  (5) obstinate
  stubborn
  (6) bookish
  formal
  stuffy
  (P)
• 固い話
  (n) serious topic (of conversation)
• 口固い
  (adj-i) discreet
  tight-lipped
• 固い握り
  (n) tight grip
• 固い約束
  (n) solemn promise
• 頭が固い
  (exp) thickheaded
  obstinate
  inflexible
• 頭の固い
  (adj-i) (sens) obstinate
  inflexible
  thickheaded
• 決意が固い
  (exp,adj-i) firmly determined
• 固いカラー
  (n) stiff collar
• 固い結び目
  (n) tight knot
• 団結が固い
  (exp,adj-i) strongly united
• 固いことは言いっこなし
  (exp) let's put formalities aside
  let's not speak so stiffly