Learn how to say Transubstantiation correctly in English with this tutorial pronunciation video.
Oxford dictionary definition of the word transubstantiate:
[with object] Christian Theology
convert (the substance of the Eucharistic elements) into the body and blood of Christ.
literary change the form or substance of (something) into something different.
late Middle English: from medieval Latin transubstantiat- ‘changed in substance’, from the verb transubstantiare, from Latin trans- ‘across’ + substantia ‘substance’