WordNet sense 1 (far-reaching and thoroughgoing in effect especially on the nature of something):

fundamental

WordNet sense 2 (important in effect or meaning):

important, significant

WordNet sense 3 (marked by depth of thinking):

deep

WordNet sense 4 (in an extreme degree):

intense

WordNet sense 5 ((of sleep) deep and complete):

heavy, sound, wakeless

WordNet sense 6 (situated at or extending to great depth; too deep to have been sounded or plumbed):

unplumbed, unfathomed, unsounded