Abarim Publications' online Biblical Hebrew Dictionary
The verb רגם (ragam) means to stone, that is to kill someone by throwing stones at that person. It's quite significant that when capital punishment was to be inflicted, the whole of the congregation of Israel was called to be the executioner (Numbers 15:35, Deuteronomy 21:21, 2 Chronicles 10:18). The surrounding nations didn't execute people by stoning and certainly not by collective effort. People dealt with in this manner were idolaters (Leviticus 20:2), soothsayers (Leviticus 20:27), and blasphemers of the name of YHWH (Leviticus 24:11).
The derivatives of this verb are:
- The feminine noun רגמה (rigma), possibly literally meaning heap (of stones) but used to describe a group of people. This word is used only once, in Psalm 68:27, and the context doesn't seem to allow a translation of stoners; that is, people who are executing someone. Gesenius believed that this root was cognate to an Arabic verb that expressed the relationship between friends, which became adopted in Hebrew in that same sense, but also to describe people joining to stone someone (strongly united friends against a weak, discordant enemy).
- The feminine noun מרגמה (margema), meaning sling (Proverbs 26:8 only).