breast poke

When one or more objects press into the breast, generally with the majority of its force being directed towards the center of the breast. The penetrating force doesn't break the skin, or otherwise breach the "skin boundary".

Some examples:

• A typical breast poke: Danbooru post #100028.
• Not a breast poke: Danbooru post #198905.
• This is a breast poke: Danbooru post #234777.

Where you may call the second image a breast poke, it is instead nipple penetration because it is breaching the "skin boundary".

This tag implicates poking (learn more).