1) to speak out, speak forth, pronounce
1a) not a word of everyday speech but one "belonging to dignified and elevated discourse"
Part of Speech: verb
Citing in TDNT: 1:447, 75
From G575 and G5350; to enunciate plainly, that is, declare: - say, speak forth, utterance.
These two sites give similar information, with the definition from several dictionaries and statistics on the use of the word.
Perseus Digital Library
University of Chicago's Logion lexicon
Thayer's dictionary plus other information.
From this site's dictionary (in Italian)
Click on the first column to search for that word as a form of the root ἀποφθέγγομαι; click on the second column to search for that grammatical form of the root ἀποφθέγγομαι; click on the third column to search for that word and grammatical form; click on the total to search for the root ἀποφθέγγομαι.