  We report on the discovery of mHz quasi-periodic oscillations (QPOs) from the
high mass X-ray binary (HMXB) IGRJ19140+0951, during a 40 ks XMM-Newton
observation performed in 201 5, which caught the source in its faintest state
ever observed. At the start of the observation, IGRJ19140+0951 was at a low
flux of 2$\times$10$^{-12}$~erg~cm$^{-2}$~s$^{-1}$ ( 2-10 keV; L$_{\rm
X}$=3$\times$10$^{33}$~erg~s$^{-1}$ at 3.6 kpc), then its emission rised
reaching a flux 10 times higher, in a flare-like activity. The investigation of
the pow er spectrum reveals the presence of QPOs, detected only in the second
part of the observation, with a strong peak at a frequency of
1.46$\pm{0.07}$~mHz, together with higher harm onics. The X-ray spectrum is
highly absorbed (N$_{\rm H}$=$10^{23}$~cm$^{-2}$), well fitted by a power-law
with a photon index in the range 1.2-1.8. The re-analysis of a Chandra archival
observation shows a modulation at 0.17+/-0.05mHz, very likely the neutron star
spin period (although a QPO cannot be excluded). We discuss the origin of the
1.46 mHz QPO in the framework of both disc-fed and wind-fed HMXBs, favouring
the quasi-spherical accretion scenario. The low flux observed by XMM-Newton
leads to about three orders of magnit ude the source dynamic range, overlapping
with the one observed from Supergiant Fast X-ray Transients (SFXTs). However,
since its duty cycle is not as low as in SFXTs, IGRJ19140 +0951 is an
intermediate system between persistent supergiant HMXBs and SFXTs, suggesting a
smooth transition between these two sub-classes.
