The poets came up with various euphemisms to describe orgasms. In the Aeneid when Venus asks her husband to forge weapons for Aeneas (8.370-406), Vulcan is initially reluctant, but then she starts touching him and he gets horny and immediately agrees to do what she wants. The scene ends with these lines:
Ea verba locūtūs
optātōs dedit amplexūs, placidumque petīvit
coniugis īnfūsus gremiō per membra sopōrem.
Carolus Ruaeus renders coniugis īnfūsus gremiō as “jacens in sinu uxoris,” and Loeb has “melting in his wife’s arms.” That’s fine as far as it goes, but from everything that has come before you can’t help but think there’s something more going on. Īnfundō, īnfundere means to pour into, so using the passive / middle, this phrase would literally be, “having poured himself into his wife’s lap,” and it’s not much of a stretch from there to see what’s being implied: Vulcan has sex with Venus, he comes inside her, then he falls asleep.
Ovid likes to speak of orgasms using the verb resolvō, resolvere, to loosen, relax, release. The syntax is venus aliquem vel aliquam resolvit, where some word for sex is the subject of the verb and the person having the orgasm the object.
Ōdī concubitūs quī nōn utrumque resolvunt. (Ars Amatoria 2.683)
I hate sex where only one of you comes.
Sentiat ex īmīs venerem resolūta medullīs
fēmina, et ex aequō rēs iuvet illa duōs. (Ars Amatoria 3.793-794)
Let a woman feel sex deep in her bones when she comes, and let that be something you both equally enjoy.
Ovid also has a peculiar instance of what cmw pointed out above about the use of ūrīnō, ūrīnāre to describe ejaculation. In Fasti 5.493-544 he tells the story of the birth and apotheosis of Orion. The setup is stereotypical: a poor but honest widower named Hyrieus offers hospitality to three wandering strangers, who turn out to be gods in disguise. When they grant him a boon, Hyrieus says that he would like a son, but doesn’t want to get married again. But now comes the pervy plot twist. [Warning: Spoiler Alert]
Adnuerant omnēs. Omnēs ad terga iuvencae
cōnstiterant—pudor est ulteriōra loquī.
Tum superiniectā tēxēre madentia terrā,
iamque decem mēnsēs et puer ortus erat.
Hunc Hyrieus, quia sīc genitus, vocat Ūrīōna.
Perdidit antīquum littera prīma sonum.
They had all nodded in agreement and gotten up to stand around the hide of the heifer Hyrieus had slaughtered, and—No, I’m not going to tell you what happened next, it’s too embarrassing. Suffice it to say that they buried the dripping hide, and ten months later there arose a little boy. Because of the way he was born, Hyrieus called him Urion. The first letter has lost its original sound.
So what happened? It doesn’t take much imagination to figure it out. The three gods Jupiter, Neptune and Mercury, performed a kind of divine circle jerk which, god semen being what it is, managed to thoroughly soak the hide (yuck), which they then proceeded to bury in the ground, and after a normal period of gestation a baby was born.