Third base

[Becky]

The third base before home plate in baseball you damn perverts.

[Sonia]

The last base before sex, entailing contact with the main sexual regions, a handjob or a blowjob (fellatio) for guys and fingering or giving head (cunnilingus) to the girl

[Tanya Shivari]

The orignal definition was touching, feeling, and assumedly handjobs. But now that society has become so desensitized to the intimacy of sexual intersourse, what with children giving birth at 11, 12, 13, left and right, third base has now been shunted up to second and the acts of [fellatio], [cunnilungus], and on occasion even [anal] sex, which have been traditionally associated with full-on sexual intercourse (i.e. making it home or [scoring]) have been placed on third base in order to enable todays alienated and cynical youth to give [blowjob]s and [eat out] pussy to their hearts content.

[Couch Potatoe]

Normally meaning to engage in digital or oral activity...But in the case of Bill our inexperienced friend having a girl sit by him.

[Tina]

Controversially debated, but the modern accepted definition of Third Base is both Fellatio and Cunnilingus.
Fellatio being oral sex performed on a male, involves a penis being placed into ones mouth, commonly known as a headjob, sucking off or a blowjob, although one generally does not blow when performing.
Cunnilingus being oral sex performed on a female, involves a tongue entering a vagina, commonly known as licking out and eating out.

[Justin Bieber]

giving/recieving head or eating a girl out.

[Donald Trump]

Getting to third base is the most ambiguous stage of high-school heterosexual interaction. The definition really depends on how far the boy goes: is it an intermediate stage followed by going all the way, or is it the final stage of making out? (everything that follows is from the boys perspective) When I was a kid (mid-70s) it meant groping skin-to-skin instead of through the clothes. Today its gone farther: getting to third implies that you eventually squirted; I got as far as third means that you didnt do it inside her (hand job, blow job, dry-hump, just lose it while making out, etc.). If you go all the way, it doesnt really matter when you got to third.

[Sonia]

Fondling her honey pot, blow job, or oral sex.

[Rihanna]

In relationship/sexual terminology, this is the Stage in dating where while making out or making love, the couple advances by heavy petting and touching, while potentially removing a few articles of clothing.
This can include touching of the womans bare legs, breasts, and hips. This can lead to the touching of private-areas.
For some, this can lead to stimulating one-anothers private regions by Touch.
In more hardcore culture, this can also include oral sex or fingering. [See also Mutual Masturbation]