Context : OB stars are important building blocks of the Universe , but we have only a limited sample of them well understood enough from an asteroseismological point of view to provide feedback on the current evolutionary models .
Our study adds one special case to this sample , with more observational constraints than for most of these stars .

Aims : Our goal is to analyse and interpret the pulsational behaviour of the B3 IV star HD 43317 using the CoRoT light curve along with the ground-based spectroscopy gathered by the Harps instrument .
This way we continue our efforts to map the \beta Cep and SPB instability strips .

Methods : We used different techniques to reveal the abundances and fundamental stellar parameters from the newly-obtained high-resolution spectra .
We used various time-series analysis tools to explore the nature of variations present in the light curve .
We calculated the moments and used the pixel-by-pixel method to look for line profile variations in the high-resolution spectra .

Results : We find that HD 43317 is a single fast rotator ( v _ { \mathrm { rot } } \approx 50 \% v _ { \mathrm { crit } } ) and hybrid SPB/ \beta Cep-type pulsator with Solar metal abundances .
We interpret the variations in photometry and spectroscopy as a result of rotational modulation connected to surface inhomogeneities , combined with the presence of both g and p mode pulsations .
We detect a series of ten consecutive frequencies with an almost constant period spacing of 6339 s as well as a second shorter sequence consisting of seven frequencies with a spacing of 6380 s. The dominant frequencies fall in the regime of gravito-inertial modes .

Conclusions :