- Concealed
- Concealed; not noticed
- Invisible
- Not noticed
- Out of sight
- See nun become invisible!
- Unnoticed
- Crept in
- Entered unnoticed
- Penetrated
- Penetrated (spy group)
- Pervaded
- Sneaked in
- of Infiltrate
- Enters by stealth
- Enters unnoticed
- Penetrates
- Penetrates subversively
- Sneaks in
- enter by stealth
- Enter unnoticed
- Surreptitiously gain access
- To enter by penetrating the pores or interstices of
a substance; to filter into or through something.
- To penetrate gradually; -- sometimes used
reflexively.