@Trevorist: "stir" is a valid translation in this context, though לבחוש might be more appropriate.
I heard some native speakers saying "mearvev" instead of "mearbev" :/ Which one is preferable?
Could that verb be considered a pi'el construction with ע-רב-ב as root? Cos we've come across many verbs with more than 3 root letters and I was wondering if we could categorise them this way or if Duo has a whole other section on "longer verbs" that I'll discover later.
Yes, the Pilpel עִרְבֵּב was formed by doubling the last consonant of the root ערב. You find it in the Aramaic part of the Bible חזיתה פרזלא מערב בחסף טינא Dan 2.41you saw the iron mixed with the potter’s earth. Modern Hebrew uses עֵרֵב in the sense of to involve: הַאִם הַתׇּכְנִית שֶׁלְּךָ מְעָרֶ֫בֶת רוֹבֶה Does your plan involve a rifle?