WordNet sense 1 (any material used to thicken):

thickener

WordNet sense 2 (any thickened enlargement):

knob, node

WordNet sense 3 (complicated in structure; consisting of interconnected parts):

complex, complex

WordNet sense 4 (accumulating and becoming more intense):

deepening

WordNet sense 5 (increasing in strength or intensity):

intensifying

WordNet sense 6 (the act of thickening):

inspissation