I cannot find the word encasteler in my dictionary. Can you please give me the English word for it.

It seems to be related to the noun " encastelure" which is a veterinary term for a disease of horses' hooves caused by the horse standing for too long in water or urine. Sounds horrible. I found this in a French veterinary text online, and of course , it did not give the English equivalent. (It's not foot rot because I looked that up also. That is "le pietin" with an acute accent which my current keyboard will not allow me to add. )

Bonjour Ron !

This is indeed a very obscure verb, referring to a veterinary condition, as Jean said above.

You could find the definition of this verb in our related lesson:
https://progress.lawlessfrench.com/revision/grammar/conjugate-eter-and-eler-verbs-in-le-present-exceptions-in-e-only

J'espère que cela vous est utile !
À bientôt !