Parablepsis is a transcription error caused by a scribe skipping over a bit of text, and thus dropping a letter, word, or longer segment of text in their transcription. It literally means 'looking to the side', coming from the Ancient Greek παρά (para-, meaning 'beside') and βλέπω (blepō, meaning 'to look').
A textual critic will generally try to identify the cause of the parablepsis; the two most common causes are homoioarcheton, in which the scribe skips from one word to a second word with a similar beginning, and homoioteleuton, in which the scribe skips from one word to another word with a similar ending.
Parablepsis is sometimes said to also include dittography, in which one repeats a segment of text, and haplography, in which one drops part of something that should be repeated. One might choose to distinguish parablepsis from katablepsis, in which one skips down one or more lines in the text; obviously, katablepsis would tend to result in longer deletions than would parablepsis. However, most people do not feel the need for this fine a distinction.
Brevity Quest 2016