Doldrums is a

The Doldrums, also known as the Intertropical Convergence Zone (ITCZ), is a belt of low pressure located near the equator, typically between 5° N and 5° S latitudes [c1][t4]. It is characterized by extremely calm air movements and a lack of substantial horizontal wind because it is a zone where the trade winds from the northern and southern hemispheres converge and ascend [c2][t2]. Historically, sailors referred to this region as the Doldrums because their ships would often become 'becalmed' or stuck in these windless waters for long periods [c2][t3][t4]. While it is a site of intense solar heating and vertical convection currents leading to thunderstorms, the surface conditions are defined by weak, light, and shifting winds, making it a 'no-wind' or calm belt within the tropics [t2][t7].

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > Equatorial Low-Pressure Belt or 'Doldrums' > p. 311
2. [2] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 14: Climate > Pressure and Planetary Winds > p. 139
3. [3] https://education.nationalgeographic.org/resource/wind/
4. [4] https://oceanservice.noaa.gov/facts/doldrums.html