Abarim Publications' online Biblical Greek Dictionary
The verb κηρυσσω (kerusso) means to proclaim, to publish verbally, but it needs to be remembered that prior to the invention of PA systems, newspapers and telegraphs and such, anything that had to be conveyed to multiple recipients rather than a specific one, had to be "proclaimed." In translations of the New Testament our verb is often translated with "to preach," but this is unfortunate since that English verb is reserved for the conveyance of moral criticism, and of course the verbal presentation performed in churches.
Quite contrary to our English verb "to preach" in the classics our verb κηρυσσω (kerusso) is used for any sort of verbal message that is loud and general, from official publications by rulers to the incentive jars of auctioneers and all sorts of summons, calls and invocations. Even the advertizing of wares and services in market places was done by means of our verb, along with the delivery of pieces of journalism and other intel that trickled in on the caravans — see our discussion of the verb ευαγγελιζω (euaggelizo), meaning to deliver a pleasant message (a.k.a. to evangelize), which is part of the larger verb αγγελω (aggelo), meaning to message, which in turn derives from the noun αγγελος (aggelos), meaning messenger, from whence comes our English word "angel."
Our verb is used 61 times, see full concordance, and from it derive:
- The noun κηρυγμα (kerugma), which describes that what is proclaimed: a proclamation or rather: the proclaimed, emphasizing the info conveyed and even the response there to, rather than the noise made. This noun, obviously, has the same wide compass as the parent verb and covers much more than simply a sermon preached. This noun is used 8 times; see full concordance.
- The noun κηρυξ (kerux), which describes someone who does the proclaiming. Since most professions in the old world required some kind of verbal projection, "proclaiming" was done all the time. Our noun, however, specifically describes someone who's job it was to make an announcement: either to announce the start of a periodical event (like an Assembly, or εκκλεσια, ekklesia), or someone who traveled from town to town to proclaim a specific message and to make sure that everybody was up to snuff with the latest goings on. In the New Testament our noun is used in 1 Timothy 2:7, 2 Timothy 1:11 and 2 Peter 2:5 only.
- Together with the preposition προ (pro), meaning before: the verb προκηρυσσω (prokerusso), meaning to fore-proclaim. This common verb was used to describe the proclamation of a future event; anything from a coming battle to some stage play, debate or the arrival of some dignitary. In the New Testament it's used only once, in Acts 13:24, where it applies to the ministry of John the Baptist.