  Stellar flares are characterized by sudden enhancement of electromagnetic
radiation in stellar atmospheres. So far much of our understanding of stellar
flares comes from photometric observations, from which plasma motions in flare
regions could not be detected. From the spectroscopic data of LAMOST DR7, we
have found one stellar flare that is characterized by an impulsive increase
followed by a gradual decrease in the H$\alpha$ line intensity on an M4-type
star, and the total energy radiated through H${\alpha}$ is estimated to be on
the order of $10^{33}$ erg. The H$\alpha$ line appears to have a Voigt profile
during the flare, which is likely caused by Stark pressure broadening due to
the dramatic increase of electron density and/or opacity broadening due to the
occurrence of strong non-thermal heating. Obvious enhancement has been
identified at the red wing of the H$\alpha$ line profile after the impulsive
increase of the H$\alpha$ line intensity. The red wing enhancement corresponds
to plasma moving away from the Earth at a velocity of 100$-$200 km s$^{-1}$.
According to the current knowledge of solar flares, this red wing enhancement
may originate from: (1) flare-driven coronal rain, (2) chromospheric
condensation, or (3) a filament/prominence eruption that either with a
non-radial backward propagation or with strong magnetic suppression. The total
mass of the moving plasma is estimated to be on the order of $10^{15}$ kg.
