Corresponding to something of lower dimension under a birational correspondence.
Forming an exception; not ordinary; uncommon; rare.
Better than the average; superior due to exception or rarity.
An exception, or something having an exceptional value
Hackneyed (lacking significance through having been overused; unoriginal and trite)
Like a hack; amateurish.
Using, or characterised by, hacks: poorly designed workarounds.
Filthy or totally dirty.
Short and interrupted, broken, jerky; hacking.