important
1 far-reaching, grave, large, material, meaningful, momentous, of substance, primary, salient, serious, signal, significant, substantial, urgent, weighty
2 big-time (informal) eminent, foremost, high-level, high-ranking, influential, leading, major league (informal) notable, noteworthy, of note, outstanding, powerful, pre-eminent, prominent, seminal
3 (usually with)
basic, essential, of concern or interest, relevant, valuable, valued, inconsequential, insignificant, minor, needless, negligible, secondary, trivial, undistinctive, unimportant, unnecessary
all-important
central, consequential, critical, crucial, essential, key, momentous, necessary, pivotal, significant, urgent, vital
self-important
arrogant, big-headed, bumptious, cocky, conceited, full of oneself, overbearing, pompous, presumptuous, pushy (informal) strutting, swaggering, swollen-headed