1) Downplay 2) Make trivial or insignificant 3) Minimise 4) Minimize 5) Trivialise 6) Understate 1) Gloss over 2) Trivialise 
[v] - make trivial or insignificant
trivialize, trivialization To reduce to triviality; devalued; to make insignificant; to treat something as, or make it appear, less important, significant, or valuable than it really is.