Looks like a peace lily that needs somewhat better growing conditions. I'd take it out of a terra cotta pot and put it in glass or plastic. They will grow in 100% water too as long as you trim the roots every few months.
no that is a Dumbcane .. (Diefenbaccia) (Sp) .. it just needs a lil more light .. and also check for spidermites .. they love this plant .. just mist and watch for webbing .. if you have some then shower the plant and rub off all the webbing and spray with a good mite spray ..
It is in fact a Dieffenbachia. I had two that went to 6.5' and 5'. They like high bright light, cooler temps, drying out of soil between waterings (or you will get root and stalk rot), light/peaty soil and fertilizing every 2.5-3 weeks. One of mine even produced a large, smelly flower (it was approx 11yrs old when it did this) You can also start a new plant easily from taking a cutting of a small leaf and putting into water and placing on a sunny windowsill. Within 2 weeks you will have roots forming. Just take care of not getting stem rot.
Please be very careful when propagating this plant or if you have to cut it back. The sap is very poisonus. I read many times that it's recommended wearing rubber gloves when working with it. Dumbcane is also propogated from the cane segements itself.
