這不

这不
zhèbu
(coll.) As a matter of fact, ... (used to introduce evidence for what one has just asserted)

CEDICT

colloquial

Entry Composition

1 這 zhè
  1. (pronoun) this; these
  2. (bound form) this; the (followed by a noun)
  3. (bound form) this; these (followed by a classifier) (in this sense, commonly pr. zhèi, esp. in Beijing)
2 不 bù
  1. no; not so
  2. (bound form) not; un-