[Delfino]

I think the simplest repeating word sentence is using "police". It isn't as impressive since it only employs two meanings rather than three but is much easier to grasp.

Who polices police? Police police. Police police police police.

But then who polices police police? Police police police. Police police police police police police.

Repeat ad infinitum. n-Police police (n-1)-police

[emptybits]

When police police police, we sometimes get oversight oversight.

[kuschku]

Wenn Fliegen hinter Fliegen fliegen, fliegen Fliegen Fliegen nach.

[nvy]

Sadly, police demonstrably do not police police.

[try_the_bass]

No, no. Police don't police police, police police police police.

[wryoak]

Because that’s the jurisdiction of the police police. Did you not read the post to which you responded?

[albert_e]

What is it called when a word stops making any sense inside your brain temporarily because of over exposure.

[omnibrain]

Semantic satiation

[iraldir]

The wikipedia page listed in another comment makes the point that this also (can) use three meanings, as Police is also a place in Poland.

The police police from Police Poland police the police from Police Poland: Police police police police Police police

[joe__f]

This makes an interesting philosophical point on ethics and self awareness