It is not completely understood what powers the extremely large energy output from a Superluminous Supernova (SLSN). However, with increasing number of newly discovered SLSNe, and in particular, with better coverage of bolometric light curves and spectroscopy from early to late times, new insights have been obtained regarding this unsolved problem. This paper presents the observations of iPTF15esb, which is a hydrogen-poor SLSN discovered by intermediate Palomar Transient Factory at z=0.224. iPTF15esb has three unique features. Its multi-band light curves (LC) show several bumps, unlike a typical smooth rise-and-decline SLSN LC. The LC undulation is most pronounced at the shorter wavelength. In addition, its LC also has a plateau lasting ∼40days, somewhat similar to that of a SNIIP. The third intriguing feature is the detection of a strong, broad Hα emission at ∼70days from the primary peak, similar to what has been seen in SLSN-I iPTF13ehe. iPTF15esb After that, it undergoes a rapid decline with Lbol ∼ t−2.5 , have two prominent bumps and a plateau with a duration of ∼40days, similar to that of a SNIIP. The LC undulation is most pronounced at the shorter wavelength. The third intriguing feature is the detection of a strong, broad Hα emission at ∼70days from the primary LC peak. reports the observations of iPTF15esb at z=0.224, which reveal three unique characteristics The multi-band light curves reveal several prominent bumps on top of a general trend of rising and declining. These bumps are most pronounced at shorter wavelength. In addition, late-time spectra display a strong, broad Hα emission, similar to iPTF13ehe. These new features observed in iPTF15esb could be explained by three different models, (1) shell-shell collisions or ejecta-CSM (H-poor) interaction, (2) changing of opacity, (3) fall-back accretion of a central blackhole with varying fall-back/accretion rates...