i Register
In some senses, subtle is marked as archaic, obsolete, US, rare. Watch for register when choosing this word.
VERBS
be, seem | become
ADV
extraordinarily, extremely, very
infinitely
Her cooking style is infinitely subtle, using just a pinch of spice to enhance each dish.
not exactly, not too
Her criticism of the new office design was not exactly subtle during the meeting.
fairly, quite, rather