1. (

• invent ,
• contrive ,
• devise ,
• excogitate ,
• formulate ,
• forge ,

) come up with (an idea, plan, explanation, theory, or principle) after a mental effort; "excogitate a way to measure the speed of light" ;

2. (

• chew_over ,
• think_over ,
• meditate ,
• ponder ,
• excogitate ,
• contemplate ,
• muse ,
• reflect ,
• mull ,
• mull_over ,
• ruminate ,
• speculate

) reflect deeply on a subject; "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" ;