talk through one's hat

talk through one's hat (to talk a lot about a subject that you do not really understand; to talk nonsense) — рассуждать глупо, неразумно, бездоказательно; ≈ нести чушь, ≈ пороть чепуху; говорить, рассуждать о том, чего не знаешь

Example: You're talking through your hat now. — Ты сам на понимаешь, что говоришь.

Example: Stop talking through your hat. — Хватит говорить глупости. Кончай нести чепуху. Хватит говорить о том, что не понимаешь.

Example: "I've heard about your honest judges," Ace sneered. "You can spot them by the smoke columns when their cars blow up." "Ace, stop talking through your hat. Let me make it crystal clear what's at stake here." (Bruce Sterling, "Kiosk")

Example:
WHALE: Oh, there may not be atheists in the foxholes, but there are occasionally lovers.
CLAY: You're talking through your hat now.
(Mv.: "Gods and Monsters" 1998)

Example: As a Maryland native who has been eating crab cakes for more than three decades, I am not whistling through my hat when I say I've never had a bigger, meatier crab cake, albeit a bit bland (which I solve with three drops of Tabasco). (Washington Post)

Related vocabulary:
[ерунда]
it's nonsense!
you are talking nonsense!
[talk rubbish]
[talk rot]
[full of baloney]

говорить ерунду; нести ерунду