Green’s Dictionary of Slang

suck wind v.

1. (US) to be on one’s last legs, to be struggling.

[US](con. WWII) R. Leckie Marines! 111: I’m going to ride you so hard yer gonna think yer rear end is suckin’ wind.
[US]H. Rhodes Chosen Few (1966) 208: Sergeant Moreau’s ass is gonna suck wind payday.
[US]J. Wambaugh Choirboys (1976) 121: She’s really got him sucking wind.
[US]Eble Campus Sl. Fall 5: suck wind – to speak in class when unprepared.
[UK]J. Mowry Six Out Seven (1994) 326: Sabby still suckin wind.
[US]C. Cook Robbers (2001) 3: Sucking wind under the onslaught of money, a stripmall gangbang straddling the Balcones Fault.

2. (US teen) a dismissive retort to someone who is showing off.

[US]H. Ellison ‘A Boy and his Dog’ in Beast that Shouted Love (1976) 206: Suck wind, asshole!
[US]R. De Christoforo Grease 113: ‘Ehey, babe, handle with care, and don’t mess the hair.’ [...] ‘Sonny, suck wind, will ya, and gimme a hug!’.

3. to show off, to boast emptily.

[US]S. Stallone Paradise Alley (1978) 40: I think ya suckin’ wind.

In phrases

have one’s face out a yard and sucking wind (v.) [one fig. gasps for air]

(US) to be a braggart.

[US]Maledicta 1 (Summer) 14: If he is particularly ignorant or foolish, and proves it by talking loudly or a lot about things he knows nothing about, his ass is out a yard-and sucking wind.