The word combinatorial is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 24
Highest Scoring Words With Friends™ Play In The Letters combinatorial
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Seven Letter Word Alert: (53 words)
abiotic, ablator, acrobat, airboat, aircool, airmail, albinic, albitic, alicant, ambiant, bicolor, bitcoin, boatman, botanic, cambial, carinal, cartoon, clarion, coalbin, coalman, coaltar, coatman, control, coolant, coronal, crabman, cranial, lacinia, laminar, libator, locator, mailcar, marconi, marital, martial, martian, martini, militar, monilia, monitor, moonlit, moronic, narcoma, octoban, omicron, oolitic, oration, orbital, robotic, tabooli, tobiano, toolbar, toolman