Sentence:  When a man "blows his <WSD>wad</WSD>," at least two different things could have occurred: he either spent or lost all his money in a wager (his wad), or he spent or ejaculated his sperm (his <WSD>wad</WSD>). Thorne goes on to suggest that since at least the 1950s "blow," in this context, is a euphemism for "ejaculate." 
Meaning of the word marked with <WSD> tags:  An ejaculation of semen.