Laahiq:

A laahiq is a muqtadi who misses a few or all his rakaats after having joined the congregation irrespective of whether he has some excuse or not. For further details refer to the chapter "Masa'il connected to the imam and muqtadi" mas'ala no. 22.

Lailatul Qadr:

Literally means "the night of power". It refers to the night in which the Quran was revealed. This night generally falls in the last ten odd nights of the month of Ramadaan.

Luqmah:

Literally means "a little piece or morsel". In kitaabus salaat it refers to correcting the imam when he commits any mistake while leading the congregation in salaat.