If something is done tackily, it is done in a way that is not stylish or in good taste.
The word tackily makes people think of bad fashion or bad decorations.
Examples:
She dressed tackily for the party.
The room was decorated tackily with bright colors.
He spoke tackily and made everyone laugh.
The cake was decorated so tackily, it looked like a joke.
The house was tackily decorated with too many lights and strange colors.
She always dresses tackily, but she doesn't care what others think.