thicken
/ˈθɪkən; `θɪkən/ v[I, Tn]
1 (cause sth to) become thicker （使某物）变得厚、 密、 浓、 混浊不清等
when the sauce thickens 沙司变浓时
The fog is thickening. 雾渐渐重了.
Use flour to thicken the gravy. 加面粉使肉汁浓稠.
Several drinks had thickened his voice. 他喝了几杯酒以後嗓音变得沙哑了.
2 (idm 习语) the plot thickens => plot2.