The word is derived from the Greek term πλεονασμός, which means “superfluous, unnecessary, redundant.”
The term is most often applied to participles in New Testament Greek, a pleonastic participle. An example of such a participle would be something akin to “answering, he said” (nb: other discourse explanations have been offered for so-called pleonastic participles of verbs of speaking. See chapter 7 of Runge’s Discourse Grammar.) or “going out, he went out.”
Yet, New Testament Greek is not the only place you will find the use of the words pleonasm or pleonastic. If you study the Septuagint, you have most likely encountered several articles on the pleonastic use of the pronoun. Since it took me a bit of time to make the word “stick” in my vocabulary and make application of the concept to examples within the LXX, I thought I might share an example I came across this morning in my studies.
A pleonastic pronoun often arises in the LXX, simply put, when the relative pronoun אשר (which) occurs within the Hebrew text. Since אשר (which, whose) is undefined for case, number, and gender, Hebrew authors will often use a pronoun to identify the previous referent for which אשר stands. Let me give you an example from:
וַיֹּ֣אמֶר אֱלֹהִ֗ים תַּֽדְשֵׁ֤א הָאָ֙רֶץ֙ דֶּ֔שֶׁא עֵ֚שֶׂב מַזְרִ֣יעַ זֶ֔רַע עֵ֣ץ פְּרִ֞י עֹ֤שֶׂה פְּרִי֙ לְמִינ֔וֹ אֲשֶׁ֥ר זַרְעוֹ־ב֖וֹ
And God said, “Let the earth bring forth vegetation, plants sowing seed, fruit tree making fruit according to its kind, which [has] its seed in it . . .
Notice how the relative particle אשר is not marked for case, number, or gender. Thus, the subsequent noun זרע (seed) contains the 3rd person masculine pronoun ו (its) as a reference back to עץ פרי (fruit tree).
How does the Greek translator handle this construction?
καὶ εἶπεν ὁ θεός Βλαστησάτω ἡ γῆ βοτάνην χόρτου, σπεῖρον σπέρμα κατὰ γένος καὶ καθ᾿ ὁμοιότητα, καὶ ξύλον κάρπιμον ποιοῦν καρπόν, οὗ τὸ σπέρμα αὐτοῦ ἐν αὐτῷ κατὰ γένος
And God said, “Let the earth put forth pasture land vegetation, seed propagating according to kind and according to likeness, and fruit–bearing tree producing fruit of which its seed is in it according to kind, on the earth” (NETS)
Notice the Greek relative pronoun οὗ (of which)? This pronoun is a neuter singular genitive. As such, the gender and number correspond to the gender and number of ξύλον κάρπιμον (fruit-bearing tree), letting the reader know that a further comment will be made about ξύλον κάρπιμον (fruit-bearing tree). The genitive case tells the reader how the pronoun functions in the sentence.
This one Greek word essentially accomplishes the tasks of two of the Hebrew words in this verse: אשר (which) and the personal pronoun ו (its). Accordingly, there is no need to translate the Hebrew pronoun ו (its). Yet, instead of leaving the pronoun untranslated, the translator renders the unnecessary (pleonastic) pronoun when providing τὸ σπέρμα αὐτοῦ (its seed) as a transaltion for זַרְעוֹ (its seed).
This phenomenon in the LXX, if I’m not mistake, results from a translator’s desire to provide a morphological equivalent for each word in his Vorlage (the original text from which he translates). Notice that the NETS translators, seeking to provide their readers with the feel of the LXX text reflects the pleonastic construction by translating with “of which its” instead of “and fruit-bearing tree producing fruit whose seed is in it . . . .”
I hope this little example helps you understand what it means for an element in NT or OT Greek to be pleonastic and how to recognize it when you encounter one.