Green’s Dictionary of Slang

missionary n.

[SE missionary position, considered the least adventurous of all the positions of love-making]

missionary position intercourse.

[Aus]‘Thommo’ Dict. Aus. Swearing & Sex Sayings 83: MISSIONARY — The sexual intercourse position most accepted as normal, with the male laying on top of the female face to face.
[UK]R. Milward Apples (2023) 119: I wasn’t sure if I wanted the whole ordeal of dating [...] all that for just a boring Missionary.

In compounds