Definition of jam-full in English:

jam-full

adjective

informal
  • Extremely crowded or full to capacity.

    ‘a bar jam-full of people’
    • ‘To Jack, Chris was not "jam-full of contradictions" but unambiguously treacherous.’
    • ‘Why, there were seventy-five hotels in that one spot alone, and all jam full.’
    • ‘I have closed off the dining room, since it's jam full of stuff I brought up from the basement, and the hall is almost full as well.’
    • ‘That night the house was jam full of men in no time.’
    • ‘The city's jam full of kids that flock there in the spring and fall, looking for jobs.’
    • ‘The UK is jam full of accents, mate.’

Origin

Mid 19th century: from jam.