Defining a new environment without spreading over two pages

I've definied an environment with

\newenvironment{definiere}{\begin{leftbar} \textbf{Definition:}\newline }{\end{leftbar}}


Unfortunately sometimes this environment is spread over two pages, where the left-bar is about 2cm long and "Definition" written as header, but the actual definition itself is on the next page.

I'm using this environment mostly like this:

\begin{definiere}
$$WMC=\sum_{i=1}^n {c_i} \label{eq:WMC}$$
\end{definiere}


I can avoid this behaviour by moving paragraphs below or above the definition, but sometimes it doesn't make sense anymore. My question is, does someone see a more elegant solution to my needs?

-
Would making it a floating environment solve your problem? –  ℝaphink Apr 27 '11 at 8:58
@Raphink: How ? –  adnc Apr 27 '11 at 9:00
Please state what you want not what you don't want, especially in the title. You want an environment which doesn't break over multiple pages? Then say so in the title. At the moment the title means the exact opposite for me! –  Martin Scharrer Apr 27 '11 at 9:06
You are right, unfortunately I can not edit the title anymore. Sorry –  adnc Apr 27 '11 at 9:08
@adnc: Of course you can edit the title: tex.stackexchange.com/posts/16729/edit –  Martin Scharrer Apr 27 '11 at 9:11

Your \textbf{Definition} is a title like a section title. Suppress the page break like \section does it:

\makeatletter
\newenvironment{definiere}
{\begin{leftbar}%

\newenvironment{definiere}{\begin{minipage}{\textwidth}\begin{leftbar} \textbf{Definition:}\newline }{\end{leftbar}\end{minipage}}