1tank 
/ˈtæŋk/ noun
plural tanks /ˈtæŋk/ noun [count] 1 a : a container for holding a liquid or gas
▪ a water/oil/fuel tank ▪ fish tanks ▪ I filled the (gas) tank before I left for Maine. — see pictures at car, scuba diving; see also septic tank, think tank
b : the amount that a tank will hold
▪ We went through a tank [=tankful] of gas on the trip. 2 : a military vehicle that moves on two large metal belts with wheels inside them and that is covered in heavy armor
▪ a water/oil/fuel tank ▪ fish tanks ▪ I filled the (gas) tank before I left for Maine. — see pictures at car, scuba diving; see also septic tank, think tank
b : the amount that a tank will hold
▪ We went through a tank [=tankful] of gas on the trip.
in/into the tank
US, informal : in or into a very bad state or condition
▪ The economy is in the tank right now. ▪ The team went into the tank [=got much worse; became very unsuccessful] last season.
▪ The economy is in the tank right now. ▪ The team went into the tank [=got much worse; became very unsuccessful] last season.
— tank·ful /ˈtæŋkˌfʊl/ noun, plural tank·fuls [count]
▪ a tankful of gas
/ˈtæŋkˌfʊl/ noun, plural tank·fuls [count] ▪ a tankful of gas
