“Just the tip” is a slang term that refers to just the tip of the penis, and may be used as a way to get a partner to agree to penetrative sex. The tip of the penis likely refers to the head or glans. It is the most sensitive part, but makes up a small part of the penis overall.
The origins of "just the tip" are not clear, although it did appear in a very famous scene in the 2005 movie "Wedding Crashers." The first reference to it in Urban Dictionary also appeared in 2005.
For people who are new to penetrative sex or aren't sure they'd like to have it, "just the tip," may be used as a way to convince a partner to allow penetration, whether anally or vaginally. The phrase is often used tongue-in-cheek, however, because it's unlikely that the penetrating partner will be able to resist thrusting, as this tends to be what makes sex feel good.
More About Just the Tip
The aim of "just the tip" may to be push a person's sexual boundaries beyond their comfort level. This is never OK. Consent is a crucial part of any sexual encounter, and coercion is not an acceptable way to gain access to a partner's body. In addition, if a partner does consent to willing insertion of "the tip," it does not mean they have any obligation to consent to going any further.
Any time a penis is inserted into an anus or vagina, contraception should be used as pregnancy and sexual transmitted infections are a risk.
Many people who are new to penetrative sex wonder whether "just the tip" counts as sex or equates to losing one's virginity. It is important to note that what "counts" as sex is a matter of perspective. What's important is that people only engage in sexual activity for which they feel ready and that aligns with their own values around sex.
