Introducing a change in a statement in such a way so as to leave out meaning understood by it and accepting such a meaning which the words may ambiguously indicate.
Tahreef linguistically means ‘changing’.
In Islamic terminology it means ‘changing a text in wording or meaning’. Changing the word of a text may or may not also change the meaning along with it.
Tahreef is of three types:
An example of this is where the innovators change the wording of Allaah’s statement:
They change the word ‘Allaahu’ (ending with a damma) to ‘Allaaha’ (ending with a kasha). Thus making Allaah the direct object to mean that it was Moosaa who was the one soaking to Allaah, rather than Allaah spooking to Moosaa.
Here the wording has been changed, and as a result of which, the meaning is also changed.
If this is recited as “Alhumda lillaahi” then the wording is changed but meaning is not changed
Such as changing the meaning of a word from its apparent meaning with no proof. An example of this is changing the meaning of the Two Hands of Allaah to mean “strength” or “blessing” and whatever is similar to this (as is done by the Mu’tazilah, Jahmiyyah and the Ash’aree.
And it is ironic how the Ash’arees change the meaning of the Names and Attributes of Allaah to something else which may contradict their apparent meanings. One of the consequences of this is to claim that the Qur’aan contains verses, the apparent meaning of which is kufr!
[Taken from Ibn Uthaymeens explanation of 'Al-'Aqeedah Al-Hamawiyyah, Pp. 24-25]