12 letters

turbinaceous turbinacious ∙ turbinations ∙ turbinectomy turbinelloid turbocharged ∙ turbocharger ∙ turboexciter turbofighter turbomachine turbomilling turbulencies ∙ turcophilism turcopoliers ∙ turgescences ∙ turgescently turgidnesses ∙ turkeyfishes Turkmenbashi Turkmenistan turkophilism turkophobist turmschädel turnbroaches ∙ turneraceous turpentining ∙ turpentinous turricephaly turriculated ∙ turrilitidae turritelloid turtledoving turtlenecked ∙

13 letters

turacoverdins ∙ turangawaewae ∙ turbellarians ∙ turbidimeters ∙ turbidimetric ∙ turbinellidae turbochargers ∙ turbocharging ∙ turboelectric ∙ turbulentness turcification turgescencies ∙ turioniferous turistaphobia turkification turquoiselike turriliticone turritellidae turveydropdom turveydropian

14 letters

turangawaewaes ∙ turbellariform turbidimetries ∙ turbochargings ∙ turbogenerator ∙ turbomachinery ∙ turnicomorphae turnicomorphic turpantineweed turpentineweed turquoiseberry

15 letters

turboalternator Turbocompressor turbogenerators ∙ turboventilator

16 letters

turbinatoconcave turbinatoglobose turbosupercharge

17 letters

turbidimetrically turbosupercharged turbosupercharger

18 letters

turbinatostipitate

20 letters

turbinatocylindrical

Words with a ∙ are valid Scrabble words (SOWPODS word list)