noun. Words written, spelled, spoken, or sung in reverse.

Can refer to reverse sentences [sentences reverse to refer can] or reversed words in a forword sentence [desrever sdrow ni a drowrof ecnetnes] or entirely reversed words and sentences [secnetnes dna sdrow desrever lyeritne].  Can also, in certain circumstances, refer to letters themselves being reversed (i.e. mirrored), but this should not be attempted by beginners.

Also Backword, adjective and Backwords, adverb. Colloquial. Used to describe written or spoken language that either reneges on a previous statement or seeks to change previous words retroactively.

ex.  President Obama’s indication that climate change is not a priority for him is backwords.