As for the meaning of 'silabbata' the meaning seems closer to what Starter suggested (a combination of precepts,rite and rituals - a life lived maintaining these that is). As for the next bit (ie it is 'silabbata paramasa'), I suspect this is the clinging to these practices but I may be inaccurate as to the Pali meaning of the term. It is important to remember that fetters (sanyojana) are things to be abandoned- hence clinging to rites and rituals and precepts fit nicely. To me it also represents very concrete thinking- 'if I do this one thing, I will get to that place'. The path is clearly more complex than that, possibly reflecting the complexity of the mind.
In any case, enjoy:
Then Ven. Ananda went to the Blessed One and, on arrival, having bowed down to him, sat to one side. As he was sitting there, the Blessed One said to him, "Ananda, every precept & practice, every life, every holy life that is followed as of essential worth: is every one of them fruitful?"
"Lord, that is not [to be answered] with a categorical answer."
"In that case, Ananda, give an analytical answer."
"When — by following a life of precept & practice, a life, a holy life that is followed as of essential worth — one's unskillful mental qualities increase while one's skillful mental qualities decline: that sort of precept & practice, life, holy life that is followed as of essential worth is fruitless. But when — by following a life of precept & practice, a life, a holy life that is followed as of essential worth — one's unskillful mental qualities decline while one's skillful mental qualities increase: that sort of precept & practice, life, holy life that is followed as of essential worth is fruitful."
That is what Ven. Ananda said, and the Teacher approved. Then Ven. Ananda, [realizing,] "The Teacher approves of me," got up from his seat and, having bowed down to the Blessed One and circumambulating him, left.
Then not long after Ven. Ananda had left, the Blessed One said to the monks, "Monks, Ananda is still in training, but it would not be easy to find his equal in discernment."