This paper traces recent theorisation stemming from the multilingual turn and brings this into dialogue with assemblage thinking, discussing the critical potential of bringing these perspectives together to explore what language is and how it is understood. The argument maps salient features of the multilingual turn which have extended the fields of applied and socio-linguistics beyond a preoccupation with separable languages embedded within a code-based depiction of linguistic behaviour. Within this body of research, we highlight the influential theoretical frames of (trans)languaging and metrolingualism, which position language as a dynamic process -- and practice -- rather than a product. We then begin to think through language/languaging as assemblage, a process which heralds an ontological shift. In so doing, we consider the ontological turn within and beyond linguistics to extend the potential of critical language studies, breaking with hegemonic language ideology via a radical reconsideration of the temporality, complexity and materiality of language.