Many small animals have evolved ultrasensitive hearing capability by detecting acoustic flow with mechanosensory hair-like structures. The highly-damped hairy structures such as the fluffy mosquito antennae are driven to move by viscous forces in the fluctuating medium, in contrast to sensing acoustic pressure with tympanal membranes. Inspired by the acoustic flow sensing of animals, the highly-damped 2D nanofiber mesh is presented here for the ultrasensitive, broadband acoustic flow detection. By evaporating 90nm Au on a freestanding electrospun Poly(methyl methacrylate) (PMMA) nanofiber mesh, we fabricate a thin layer of conductive Au-PMMA nanomesh with dimensions 8 mm x 8 mm, with thickness of approximately 3 mu m and average fiber diameter around 430nm. The nanomesh is shown to move instantaneously with broadband fluctuating airflow near maximum physical efficiency from 100 Hz to 10 000 Hz, i.e. v(m)(esh)(t)/v(air)(t) approximate to 1, surpassing the frequency response and efficiency of previously-reported microscale hairy structures. By transducing the motion of the nanomesh with electromagnetic induction, we demonstrate fluctuating airflow detection with almost full fidelity in the measured frequency range. Sensing flow with highly-damped nanomaterials will benefit miniaturized flow measurement and sound detection, and provides an important application for the diverse flourishing nanomaterials, such as 1D nanofibers, 2D nanomeshes, and 3D nanolattices.