Abarim Publications' online Biblical Greek Dictionary
The verb βρεχω (brecho) means to rain and is used pretty much the same as the equivalent in English, including a third person singular form to say that "it" rains. The classics predominantly use the verb υω (huo) for to rain, and it's not immediately clear how this verb differs from βρεχω (brecho). But from the verb υω (huo) comes the noun υδωρ (hudor), meaning water, which suggests that υω (huo) typically speaks of watering, whereas βρεχω (brecho), more broadly, may speak of being flooded by or inundated in wealth, light, tears (Luke 7:38), or chunks of burning material falling from heaven (Luke 17:29).
Our verb βρεχω (brecho) may also describe how sponges (or heavy drinkers) are soaked, which suggests that υω (huo) focusses more on the water falling from the sky, whereas our verb βρεχω (brecho) focusses more on whatever becomes over-saturated with whatever floods it, from whichever source.
Our verb βρεχω (brecho), to inundate, is used 7 times in the New Testament, see full concordance, and from it derives: