1. reflect deeply on a subject
e.g. I mulled over the events of the afternoon
philosophers have speculated on the question of God for thousands of years
The scientist must stop to observe and start to excogitate
Synonym: chew overthink overmeditatepondercontemplatemusereflectmullmull overruminatespeculate
2. come up with (an idea, plan, explanation, theory, or principle) after a mental effort
e.g. excogitate a way to measure the speed of light