1) a viper, snake Part of Speech: noun masculine A Related Word by BDB/Strong’s Number: from H659 (in the sense of hissing) Same Word by TWOT Number: 1791b
Brown-Driver-Briggs
אֶפְעֶהnoun [masculine]a kind of viper (Thes 'a flando et sibilando;' compare Arabic viper, Ethiopic id.); — ׳אIsaiah 30:6; Isaiah 59:5, ׳לְשׁוֺן אJob 20:16.
Job 20:16 HEB:תַּֽ֝הַרְגֵ֗הוּ לְשׁ֣וֹן אֶפְעֶֽה׃ NAS: of cobras; The viper's tongue KJV: of asps: the viper's tongue INT: slays tongue the viper's
Isaiah 30:6 HEB:וָלַ֣יִשׁ מֵהֶ֗ם אֶפְעֶה֙ וְשָׂרָ֣ף מְעוֹפֵ֔ף NAS: and lion, viper and flying KJV: and old lion, the viper and fiery INT: and lion where viper serpent and flying
Isaiah 59:5 HEB:וְהַזּוּרֶ֖ה תִּבָּקַ֥ע אֶפְעֶֽה׃ NAS: And [from] that which is crushed a snake breaks forth. KJV: breaketh out into a viper. INT: is crushed breaks A snake
viper, Ethiopic 
id.); — ׳אIsaiah 30:6; Isaiah 59:5, ׳לְשׁוֺן אJob 20:16.