大事な話 — [We have to talk to him. This will be] a

大だい事じ な  話はなし

[We have to talk to him. This will be] an important conversation.

hanashi: conversation, talk

Card 70 of 2,076 in Tae Kim's Japanese Grammar.

More from Tae Kim's Japanese Grammar

きれい な  先せん生せい だった なあ

妙みょう な やつ

Note the long o, which results from yo + u

大だい事じ な  友とも達だち

俺おれ が  行いく

すてき な  花はな

大たい河が が  好すき だ

"taiga" is the name of a character.