The acoustic response of a passive single point scatterer under grazing flow is shown theoretically and experimentally to have both monopolar and dipolar contributions. The monopolar response is dominated by the pressure-induced flux Q_p , which is related to the specific acoustic impedance of the point scatterer as \zeta=-1/Q_p . By contrast, the main dipolar response is the pressure-induced force F_p, which is experimentally proven to be modelled by introducing a complex-valued factor \eta. In fact, \eta is related to the ratio between Q_p and F_p. By employing these two complex-valued parameters \zeta and \eta in the proposed theoretical transfer matrix model, the scattering properties of a single point scatterer (e.g., a Helmholtz resonator) subjected to grazing flow can be well predicted. This model can be readily used in practical applications such as the design of passive absorbers and silencers in ventilation systems.