whopper, a really big one [noun] [de joekel, de joekels] [‘joe-kul’]

"Joekel" is used informally to refer to something of great size. This can be practically anything. "Joekel" is often used in the common construction "een joekel van een …", see the Examples.

"Joekel" can sometimes have a sexual connotation. The singular "joekel" would be the male genital organ, whereas the plural "joekels" would refer to a woman’s sizable breasts.

By the way, a Burgerking "Whopper" is not a "Joekel", but just a "Whopper":-)

Examples:
– "Ik heb nog nooit zo’n grote spin gezien, wat een joekel!"
("I’ve never seen such a big spider, what a whopper!") 

– "Ik had gisteravond een feestje, nu heb ik een joekel van een kater…"
("I had a party last night, now I have a really big hangover…")

– "Zo moppie, jij hebt lekkere joekels!" – "Oprotten viezerik, of ik bel de politie!"
("Well sweetie, you have a nice set of knockers!" – "Piss off you pervert, or I’ll call the police!")

Related words:
– "Kanjer": synonymous to "joekel": whopper. Also used to refer to a person of great character/skills.
– "Groot": big, large.