What is meant by “take off stage” in economics?

Take –off stage is the third stage of Rostov’s economic growth model where a country attains a self-steady and self-sustained growth. Industrialization increases with workers switching from the agricultural sector to the manufacturing sector. Growth is concentrated in a few regions of the country and within one or two manufacturing industries. The level of investment reaches over 10% of GNP.

Or

The take-off is defined as the interval during which the rate of investment increases in such a way that real output per capita rises and this initial increase carries with it radical changes in production techniques and the disposition of income flows which perpetuates the new scale of investment and perpetuate thereby the rising trend in per capita output