The best way to learn proper English is to read news report, and watch news on TV. Watching TV shows is a great way to learn casual English, slang words, understand culture reference and humor. If you have already watched these shows then you may recall the words used in the following dialogs.

I thought it ended at CUCKOO.
The Big Bang Theory Season 1, Episode 15

Oh, yeah. The Mr. Spock CUCKOO clock.
The Big Bang Theory Season 10, Episode 10

It's like the world's
fattest CUCKOO clock.
The Big Bang Theory Season 7, Episode 23

I always thought
I was more like a CUCKOO bird.
The Big Bang Theory Season 1, Episode 15

The newly hatched CUCKOO
eats all the food...
The Big Bang Theory Season 1, Episode 15