Is a word "indefatigable" a jaw-breaker? Please help me understand a dialogue correctly

Vote now!

Hello there! I'll be glad if someone could help me. I'm wondering if a word  "indefatigable" is sort of a jaw-breaker? I'm trying to translate a dialogue between two characters. First of them is describing another one. Second character is injecting funny remarks into that rant.

1st: He's (this and that), he’s got your back... Just when you need him he’s there...
2nd: Well, sure... It's true...
1st: Need help with diction?
2nd: Indefatigable.

 So, what he meant exactly? "I'll teach you to pronounce a tongue twisters and  the word "indefatigable" is an example" or "You have to work hard. Do it indefatigable"?