From gross + -ish.
grossish (comparative more grossish, superlative most grossish)
- (rare) Somewhat gross
2010, Rebecca West, A Train of Powder:[…] and the proper place for a caricature of Bismarck seemed to them a grossish comic paper, and not a schoolbook.
2011, Bill James, I am Gold:And then the cousin: 'LionelGarth Field, slobbier than Egremont. Grossish face.