Impenetrable

How to spell impenetrable

12 letters · 5 syllables

How to pronounce impenetrable

Say the part in capitals loudest.

What does impenetrable mean?

1. adjectiveImpossible to pass through, pierce, or enter.
2. adjectiveImpossible to understand or make sense of.

Impenetrable in a sentence

• The castle walls were thick and impenetrable even to cannon fire.

• The tax legislation was written in impenetrable legal jargon.

• The jungle grew so dense that the path became impenetrable.

• His handwriting was so cramped it was almost impenetrable.

Where does impenetrable come from?

Language of origin: Latin

This word comes from the Latin impenetrabilis, which combined the negative prefix in- (meaning 'not') with penetrabilis, 'able to be pierced'. That second part was built on the verb penetrare, meaning 'to enter, to pierce, or to pass into', which itself drew on penitus, 'deeply' or 'right inside'. English took the word in during the late 1400s, at first describing dense forests, thick walls, or armour that no weapon could pierce. Over time it grew a figurative sense as well, so that a confusing book or an unreadable expression could also be called impenetrable. The shared penetr- root still links it to the everyday word 'penetrate', and remembering that connection helps with the tricky unstressed middle, since the -etr- is the same cluster you hear in penetrate.

How the word is built

• im- (not)
• penetr- (from Latin penetrare: to pierce or pass into)
• -able (capable of being)