Attested with both -a- ‘to mix, to mingle’ and -i- ‘to be mixed, mingled’ stem vowels (Lane:1021). Note the meaning shift ‘to be mixed’ > ‘to be confused’ (ibid.)
In Gulf and Yemeni dialects this root is reflected as rbš due to palatalisation *k > š (al-Iryani:341, Qafisheh:251, Behnsted:424, 1386). Forms with k are attested in the dialect of Manāḫa (Behnstedt:1386).